Why I lose to much lower rated player ??

When? On this site?

I don't see it in your recent history. I don't see any losses to anyone ranked that low in blitz, even when you were much lower rated yourself.

You did have three losses to 1600 rated players in bullet earlier this month but you are only rated in the 1800's in bullet.

Certainly, there were no losses to 1200 to 1300's. at least not here.

the games was played 2 weeks ago on another site .. I makeda new account there and started playing and  lost 3 matches ..  

but i understand .. it make no sense posting this here .. games was plyed on other site.. I will delet the post 

"Never underestimate lower rated players".

OK, I just tried to post a Nimzovich quote which is highly relevant to this subject, and I got a message "Your post seems to not fit our Community Guidelines.  Repeated violations may result in your account being restricted.  Thank you for helping Chess.com stay a fun and friendly place for all!"

No restrictions please.  Ban or no ban.  I request that the moderators look at the comment I tried to post and decide accordingly. 

If you lose to a lower rated player is probably because you should be lower rated.

Sometimes when I play lower rated players, I play worse, it's like I'm playing at their level.

I'm reminded of: "Warum muss ich gegen diese Idioten verlieren?" - Nimzovich

We must beware of becoming complacent or sloppy when we believe our opponent is weak.

Cause sometimes we are too sure of ourselves

We are too often too sure of ourselves.  This is part of human nature.  We need to be over-confident, otherwise we would not take enough risk.  Risk-taking by individuals is good for the species.  Even though the risk-taking individual often gets hurt, the species learns useful information or lessons. 

Another way to say it: we need to be over-confident, because if we really understood how little knowledge and control we actually have, we would become discouraged and take less risks.

Psychologists even have a name for this tendency of human individuals to over-estimate one's own strengths, and under-estimate (or overlook) one's own weaknesses.   See Dunning-Kruger effect:

 https://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

Many 1200-1400 are good enough to take advantage of sloppy play from arrogant 1700-2000, if you try to troll them or play the bong-cloud you may be surprised . Also I've played many unrated games against strong players and they don't seem to manage time as well as intermediate players. And if your playing unrated some people play mostly unrated and are therefore very underrated. I'm somewhat of an example, I'm more like 1400-1500ish but I play unrated because I don't like the stress of losing rating points. I also tilt pretty badly in longer matches like 5 or more.

That is probably the dumbest thing I've read today. There are so many other factors that come to play. 

I said "probably" didn't I? So I did take into account those factors

You win some and lose some, it's chess.

I struggle against lower rated players too. Very frustrating to beat 1800 with no problems, but losing to 1200’s and 1400’s. It takes a huge bite out of my rating each time.

Toviya  you lose because you keep making the same kind of mistakes over and over again.  find out your mistakes and then avoid repeating.

You’re right, of course. I don’t play enough or study, and I’m constantly trying new openings without learning them. That’s part of it. I need to take chess seriously if I want to improve.

me also we are in the same boat toviya

I completely agree with you on this one.. I can play really well against higher rated players.. but when it comes to the majority of the lower rated people in my current rating range.. I get destroyed by their mindless moves. You'd think with my experience I should know how to get around it.. but there's just so much going on that I stop knowing what to do. They don't give a crap about their pawn structure.. or yours, they just take take take.. trade and chase pieces like a rabid dog at a park full of children.. if they catch tunnel vision on a piece, they'll do anything in their power to take it. I often play the sicilian.. or try to anyways. They usually go for the bowdler attack and next thing you know,a random move outside of the book and often I am lost.. Especially when it comes to playing the pirc and they start throwing everything at me mid development *sees that I developed my knight*---*Throws the bishop and a handful of pawns at it* like..it's insanity! I don't get 400-1000 rated players sometimes (hell, I don't even know where I stand at this point, but I can show a bunch of amazing games of mine to get an idea if necessary) but yeah.. losing to players far below my own rating drives me nuts