Help me please !

I am a little bit confused. I thought that it was not considered necessary to calculate in one's head in correspondence chess. If that is what you did, you may have been giving a considerable advantage to your opponent. I am not sure what "15m 10s" is, but, even if it is not Blitz, it sounds like it is still a speed that strongly favors those with more experience. I hope that you have a satisfactory experience with the 30/30 games.

"... Most internet players think that 30 5 is slow, but that is unlikely slow enough to play 'real' chess. You need a game slow enough so that for most of the game you have time to consider all your candidate moves as well as your opponent’s possible replies that at least include his checks, captures, and serious threats, to make sure you can meet all of them. For the average OTB player G/90 is about the fastest, which might be roughly 60 10 online, where there is some delay. But there is no absolute; some people think faster than others and others can play real chess faster because of experience. Many internet players are reluctant to play slower than 30 5 so you might have to settle for that as a 'slow' game." - NM Dan Heisman (2002)

https://web.archive.org/web/20140627010008/http://www.chesscafe.com/text/heisman12.pdf

When I joined the Military about 20 years ago I had the wrong outlook when it came to military bareing.  Perhaps if I had asked questions or sought out the help I wouldn't have had to exit the Military like I did some 2 and a half years later.

The situation with you is the same.  You have the wrong outlook when it comes to making blunders and getting nailed at chess.  The last tournament I was a part of, I faced 2 NM's!!  And I was black both times!!  I could have been oh man woe is me but I played those games with the outlook that I will be getting very instructive losses.  I did get two instructive losses.  When you lose, you learn.  When you get hammered, you learn even more, especially if you can get your opponent to do a post-analysis with you.

I know it's not as easy as just saying you have to change your outlook.  You have to come up with a plan to go about it.  All I can tell you is that you have to take ego out of the equation.  So what if you lose?  You have to not care about results, and only care about learning chess.  That's how you will grow.  You're not going to have a lot of wins at first.  You have to wade through the mud like all of us have.  At my level, I lose a lot too.  I haven't been able to cross the 1600 barrier in quite some time, and as of now I am below 1500 again in blitz.  I know blitz really shouldn't be my focus, but I've been brain damaged already by too much blitz so it's okay.  I cannot tell you how many times I lost because of stupid mistakes.  Thing is we can't control if we are going to make a blunder or not.  All we can do is train our minds to try and find the best possible move every time you make a chess move in a chess game, because the second you stop making the best move you can come up with, is the second you will lose the game.  At the beginner level you lose a lot of games because you have no opening repertoire and are making random moves and fall to common opening traps that even beginners like you know.  If you don't keep a journal and drill those mistakes daily until you got them down pat, you are liable to make the same mistakes in the future.  I know someone that fell for the same queen trap more than 3 times.  The same opening, the same queen trap, and he fell for it more than 3 times.  That's not the only thing beginners have to worry about.  Hanging pieces.  Outright giving away the game here and there, the other person missing it.  It's a series of miss fires and in the end, the person who made the last blunder loses.  There are a lot of missed tactics.  That's why most people stress to do tactics daily.  Do a least 30 minutes of learning mode on chess.com, at puzzles at the rating range of your choice.  Take your time to do the puzzles.  It's okay if you only do 3 puzzles a day.  3 puzzles a day for a year is 1095 patterns learned.  That could be a good start.  I personally think tactics should be done in multiple stops.  Like for example 1.)  30 minutes of tactics trainer 2.) Some time on a tactics book  You can stop there or go further if necessary.  I know of someone who is a Master who said he used to study tactics for about 3 hours a day.  If you want to get good at tactics, you have to put in the time.  As I write this I am procrastinating on doing my tactics grind that I know I need to do before my next tournament.  The other part of it is knowing how to come up with a plan, and that's where master game study comes in.  I know I have been saying study master games in these forums till I am blue in the face but it's true.  That's where we get our ideas, from masters, not from people "a little bit above our rating..."  If you think the latter than more power to you, but I'd have to disagree.

One thing you have to do is own up to the fact, that there are Slow chess thinkers, and Fast chess thinkers.  You could be below 1000 and still be a fast chess thinker....  You have to honestly answer the question, which one are you?  There are other questions you'd need to ask, but I can't tell you the questions because they are questions in a chess book I am reading.  If you want to seriously assess yourself, and want a set of questions to ask yourself, to assess your chess, then Why you lose at chess, by Fred Reinfeld, is the book for you.  He teaches all the elements of an attack in that book, and much much more.  I know someone else said Fred Reinfeld isn't a good author, but I got a lot out of that book.  Maybe you can too!  Or not!

There is one thing I didn't mention.  The biggest factor of them all.  Consistency.  If you don't play chess every day or do your daily tactics you get sloppy, plus you don't learn new things because there is nothing to learn from you didn't do anything.  At the bare minimum.  you should do your 3 tactics trainer puzzles on learning mode daily, play one long game, (analyze your loss once by yourself then with the computer) and study one annotated master game.  On days you want to do more, but do the bare minimum, every day, because, as I said, consistency is key.  I haven't been consistent with my studies for the past 10 years or so, look where that has gotten me...

Tactics

Master games

Consistency

Play at least one game a day at a long time control so you have enough time to think about multiple candidate moves and their replies.

That's the drumbeat of success

The last one may be almost as important as consistency because that is where you are learning real chess.

I have one more thing to say in regards to losing.  The way I learned chess, was by playing a person over 500 points higher rated than me.  I learned a lot, about losing, but I also got better at chess...

If you are putting forth a lot of effort with no improvement then yes you should look to change something, but the chess.com forums are not the best place for finding answers.  Sure you will get book lists and advice.  I saw some good advice for you, but, ultimately, you are the one that has to come up with a plan to get better, or hire someone to do it for you.  

Just a thought.  If you try and try and try and do not get better, it might be possible that chess just isn't your thing.  You know that could be it, or not.  I don't know, I'm just speculating.  I have no idea about those sort of things.  If you enjoy chess then I say play it, but if you arn't satisfied when you are unable to get better, even after a lot of effort, then perhaps maybe it's time to find another hobby.  I'm not saying quit chess.  No no no.  I'm saying, you have to make a choice.  Are you going to figure this out?  Are you going to keep trying?  Do you love playing chess?  Do you want to improve?  If you love the game and want to improve then I say keep trying, and find a coach.  If you can't afford a coach, save up for it, then hire a coach.  If you can't save up for it, then your options are limited.  There is a vast amount of free advice, and a lot of free resources.  There are free databases.  Chessbase is the best, but expensive.  There are people that know how to get free ones.  Ask around.  Ask specific questions, not just, Oh I can't get better.  There is another area in my life that I am bad at and I kept telling people why I can't.  Then I learned it's time to start doing, wading through the mud.  No matter what area you are improving in, you always, have to wade through the mud, especially in chess.  

About 17 years ago I was a lot less talented as a chess player as you are, and due to playing only blitz, and not studying on my own, I didn't improve much, but I improved.  It took time.  Some people can get better and become Masters just by playing a bunch of blitz.  The rest of us can't.  I came from a worse place then you, and I know, even my, having a mental disability, can get "this" good at chess, I can't see why you "can't."  But stop telling us why you can't.  Start trying to make the change, or get out of chess.