I followed your advice and decided to play only 4 or 5 tables at once. With this number, I can adjust to my opps and, in the same time, I am not losing concetration because of long delays between "playable" hands.

Today I played only about 700 hand and I didn't run very well. Despite this fact I am pretty excited about this session, because I was able to avoid tilting and even though I was down nearly 3 BI in one moment, I managed to get it all back and ended up in blacks.

Some thoughts I figured out today:
I really need to stop barreling OOP, when I feel something ain't right
I REALLY need to stop calling insane river bets with little showdown equity... I take this for my biggest leak and I guess, this is the problem, which costs me the biggest deal of my money..
I must protect my made hands with much bigger bets... If someone is going to draw, he has to pay awfully...
when SB tries to steal my BB, I call him, float him on flop and he gives up, I must fire at least 3/4 of the pot... I must convince him that even his draws don't worth it... often he is likely to fold and I can't afford him drawing on straigh or flush...
And I should lay down my made hands more often, especially in raised pots, when opps are giving out bets like a crap...