Is there any type of position that you don't feel comftareble playing? If so that's probably a good place to start.
Assessing your strengths and weaknesses

I don't think I'm over 1800 either but perhaps, go over your games with a computer (there is even a computer analysis feature on this site) and see which moves the computer disagrees with you.
I'd bet you already tried this but I thought I'd say just in case.

Is there any type of position that you don't feel comftareble playing? If so that's probably a good place to start.
I actually feel relatively fine in open or closed positions, Opposite side castling I struggle with a little, but it doesn't come up too often. I'm good at converting endgame advantages of any type. I understand what makes a minor piece strong vs. weak. So, I don't really know what else I need to work on.

I would be willing to bet you aren't as good at king and pawn endgames as you might think. If you don't like opposite side castling you probably need to work on some tactics. I haven't looked at any of your games. But, take a look at them (especially the games you lost). Why are you losing? Strategical errors, positional, missing a tactic etc. The only way you can figure out your weaknesses is look deep into your games. It is best if you look at them with fresh eyes(as in not right after being played-you tend to have a bias right after playing them)
A pretty good general rule is if you don't like something you probably need to work on it(unless you are like me and just hate being bad at anything)

I actually feel relatively fine in open or closed positions, Opposite side castling I struggle with a little, but it doesn't come up too often. I'm good at converting endgame advantages of any type. I understand what makes a minor piece strong vs. weak. So, I don't really know what else I need to work on.
I looked at some of your games, and give some maybe useful advice below. What it really comes down to though (as other have said on the forum) is being critical of your mistakes and honestly looking at your losses. You (or anyone) don't play poor moves because you were distracted or took less time that day, you play poor moves because you misunderstand the position.
I'd almost say your attitude regarding your own ability is enough to create a rating wall at any level. What I mean is you say you're good at openings, endgames, tactics, and strategy and you don't know what else to work on, you go so far as to say you can convert an endgame advantage of any type!! That's an incredible achievement, even GMs struggle with all kinds of endgames yet you don't struggle with even one.
You play some good moves but on other moves it's like you totally forget the position and just play some non-move like there's nothing going on. In some other games you miss not so hard tactical shots... be sure when an opponent has undefended pieces to check any forcing moves you may have on an analysis board.

Hmm looking at the game again I might see your point of view a bit better. Take after black's move 25...Rhc8. It seems like you've overprotected c2 and d5 and may be a bit scared of your opponent's rating and just hoping that a fortress and shuffling around will wear him out -- when in reality your position is more free than you think. Ng3 with Bf1 and you're doing fine, there's not need to let him push you into total passivity which is dangerous, remember your position has ideas too.
Later in the game when he pushes a4 and captures on b3 you should have really recaptured with the c-pawn (then or in many other positions if he had pushed it). It looks scary opening up the file for his rooks, but you had the important squares covered. I think you had a lot less to fear from black's position through the game than you may have thought at the time.

Thank you for your analysis, I guess my last sentence made it in my last post "so, I don't really know what else to work on" came off wrong. I'm by no means implying that I know everything, I think I'm pretty weak at openings, however, I think there are other parts of my game that I need to work on first. I work on tactics every day with tactics trainer and I dont pass those at 100% so I know that I need work on tactics.
I thin orangehonda might be on to something. When I play a higher rated opponent I put my self in to a place of pasivity, I have been looking at several of my other games and I think that might be one of my biggest problems. I also see that I'm still making big blunders. I'm not hanging pieces, but sometimes I forget to take a piece hung by my opponent. Or I step into a 3 move combination that I see after I press the submit button.
Thank you again for the remarks.

So what do you do if you're just all-round terrible? How do you decide what to focus on?
Chess seems to me to be less directly intuitive than, say, sports, where it's rather easy to assess your weaknesses (you're fat and can't run, the ball keeps rolling over your feet etc). People always say to analyse your games, but how exactly do you analyse your games if you don't understand how to play in the first place?

So what do you do if you're just all-round terrible? How do you decide what to focus on?
Chess seems to me to be less directly intuitive than, say, sports, where it's rather easy to assess your weaknesses (you're fat and can't run, the ball keeps rolling over your feet etc). People always say to analyse your games, but how exactly do you analyse your games if you don't understand how to play in the first place?
This is kind of what I meant by posting this, although I woulnd't use the word terrible.

Openings. Pick one you don't know, don't like, or are not comfortable playing.
Variations of said openings.
Opening traps maybe. The traps are not so good with regards to actually working in a competitive game but they do lead to a better understanding of the opening in question. Some catastrophic moves in the openings can appear very natural.

When you say you've been stuck at 1800 for a while...how long is "a while"? I ask this because some players (especially younger ones) bemoan the rut they're in, and then I find out that they've been at the same rating for three whole weeks or something. At which I just kind of have to shake my head and lol.
About 6 months or maybee alittle longer.

I did the same thing. I was complaining that I wasn't improving. Then, taking a look back at how long ago it was since I could note a considerable difference...2 weeks. Good stuff lol
To work on things that you need improving, there are only 2 ways of this:
1. Have someone else spot the weaknesses, computer or friend or w/e
2. Know for yourself what it is.
Then work on it. Not sure what other options you were thinking you could get.
How do you decide what areas of the game you should concentrate on and improve? I've been stuck at ~1800 for a while and I've studied several different things, lots of tactics, strategies (ie. superior minor pieces), endings, openings, but I can't seem to break free of this ~1800 zone. It's like I hit a wall and I'm not sure how to break the wall down.
I think one thing I've been doing is relying to much on the game explorer, so I will end up following a line and not know why I'm following it. I end up in a complex position in which one strategic error can make or break you. So one thing I am going to do is not look at the game explorer durring my turn based games, only look at it after for analysis purpose.
I was wondering if there is any other advice that can help me break through the 1800 wall. I look forward to hearing everyones comments.