My question has a couple of pieces, and yes it's born of frustration. I've been losing steadily. I play tight and aggressive at loose, passive tables, strictly NL so that I can protect my good hands, generally with pot-size bets.

It doesn't work. I keep hearing about how I should stick with it -- it works over the long run. What is that exactly? I had thought if your bankroll was 500 big bets you could endure even the worst swings. Well, that's not the case. I swing from $300 to $9

Second part of the question: what's most important? table selection? calculating the odds? reading the other hands? guts?

My theory is that different things are most important at different moments. But I would more frequently give weight to your read on other people's hands.

-your table selection wisdom means precisely dick if you can't punish the loose players who chase or call holding the second best hand.
-your calculation of the pot odds you need are a waste of time unless you're right about what you're up against
-your courageous big bets, on top pair and ace kicker will kill you if you don't realize the other guy hit 2 pair

So the last part of the question is: how do you read other people's hands?