::My speed and calculation..::

Remembering how the pieces move.

Seriously.

I lost one rated game to a FIDE master (won the other one ) because I forgot that Pawns can't move backwards.

Playing a game sleepy and still think i can win.

Watching tv when my opponent blunders as they are more focused i am not.

Vote Chess in a 3 day / move and in winning position and the opponent will resign even when they have no chance to win or draw. Have to remember the correct move to mate in 5. If not it is a wasted move and 6 days are wasted in which i could have gotten a game in or 2 maybe.

I think endgames are the hardest to play for an amateur, I remember Nimzowitsch said that endgame technique was the main difference between good amateur players and professionals, although nowadays opening preparation is a big factor as well.

Getting myself in cramped positions

I totally agree. But the problem is that endgames are very dry and boring to learn, that is why my weakest spot in a game is the endgame. If i would study endgames more my fide rating would be over 2000. I play in Canada so we have a different kind of rating system. We have the cfc rating systen, but we also have fide, but canada is not so strong at chess, as many other countries.

A ton of moves yes, but most of them aren't any good. It sounds stupid but talking to yourself (internally of course) is a good way to handle end games. Forget about calculating variations, say things like 'must keep my rook active, even if I have to give up a pawn' or 'If I can get the bishops off, the pawn ending looks winning' or ' got to activate my king and get the centre pawns rolling' etc,etc. The endgame is about plans more than variations...of course if you can't tell the difference between a won or lost ending then its all irrelevant!