tips for chess concentration improvement???

hello... I am 1300-rated rapid chess player..... I have noticed that I have lost many games due to simply "snapping out" of my deep concentration in the endgames.....I end up actually blundering like a 500-rated player....and it really makes me angry.... it all starts if someone dares to enter my room while playing....and just like that...I usually lose all my efforts in the past 40 minutes!! I know the general tips about concentration improvement (eat and sleep well......don't play many games in a row....don't play at night unless you can't play in the morning....etc..) but....is there any more to know?? after all....even after following these rules...my situation hasn't improved really much.... can anyone really tell me some more...probably chess-realted...tips for concentration???

it also takes me a huge effort to re-calculate my future moves once I lose that chain of thoughts....eventually leading to a total collapse....help??

I must admit...your advices are interesting and actually good....thanks....however that doesn't change the fact that you over-confedence is insulting...

Exactly....

 

I accept your challenge on one condition....

You take back your reckless claim if I win..