When game progreses I tend to make more and more blunders.

Thanks for all the comments
I had no idea there are so many blunders after move 310. (Maybe I should study endgame someday:P) blunder that i find very stupid is move 299, instead of connecting the two stones...

Checklist might help, especialy when I have enough time.
EdLee:
I think I make more blunders later because moves are not that interesting and
I have already made many moves. And I lose concentration.(Which is odd because I have very good concentration for physics, math but I find that different kind of concentration somehow)
(Difference in ranks is not 4 stones(more like 2), my ranks have not convergated(just made the Tygem acc))

I kind of expected that playing many games under time pressure will help but nobody suggested that so sloving this problem is apperently not so easy.

So I will try to save some time for endgame and think about moves and ask myself: is it a blunder?

Another thing i must try is if I make more/less mistakes if I try to play seriously/ not so seriously

In the future, it may be possible to purchase an EEG-like device you can wear on your head which will warn you of an increased probability of blunders. See Using EEG to Scan the Brain for Impending Error.

There are other examples you can find, because fatigue-related errors are an active area of research.

From a practical point of view, I think there would be some kinks to be worked out before using this in an OTB go game. The normal implementation, such as flashing a light or playing an alert sound, would not be desirable as it would be the worst tell ever. I can imagine wearing one of those things in a game and then, when the alarm goes off, my opponent would immediately smile and start making overplays...

I suppose it could be helpful for online games, though.

...

One low-tech feedback device for stress that violinists have used is a wine cork held between the teeth. Often players are surprised when they bite through the cork.

One low-tech feedback device for stress that violinists have used is a wine cork held between the teeth. Often players are surprised when they bite through the cork.

Does the same work with stones instead of a wine cork ?

I made a couple of edits. Nothing you were not aware of after the game, I am sure.

Fatigue can be a problem. It might help to eat a power bar or something. Mental fatigue can be cured by a brief rest. Even a matter of seconds can help. Do you get tense when you play? Relaxation, as Robert said, can help.

You might enjoy studying the endgame. Lots of things you can overlearn.

I don't know if asking yourself if your play is a blunder is such a good idea. It shows a negative mindset. Better to ask yourself what your move accomplishes. (Endgame study can help you answer that question quickly and reliably. ) As Kotov suggests, ask yourself what your candidate moves are. That question will help you to avoid overlooking a play.

Something that helped me, both with relaxation and with not overlooking something, was to take a second or two before making my play and just look at the whole board. In that relaxed state of mind I could sometimes see good moves that I had missed while focused on reading a small region of the board.

...
On a more serious note, I think it's great that the term "blunder" seems to have a clear usage in this thread. I think it's important to distinguish blunders, i.e., mistakes far beneath the players expected strength, from ordinary mistakes. I agree with others that there are no easy fixes. Trying to hard to avoid mistakes might make one's play too conservative, which itself can be a mistake depending on the position. Even for mistakes that are fairly below our level, some will slip through simply due to time constraints.
...

How to lower blunder rate?