Sports Psychology and the art of feeling good about yourself....or not

Confession time: I struggle with a committee in my head (and I've tried to ignore 'em) that tells me things like...."you suck"..."you'll never get any better", blah blah blah. Now that BillS has encouraged me to delete that dreaded work from my lexicon, I am sure that another one will pop up. I know this is kind of a rant....but how does one really feel good about themselves as a swimmer yet avoid being delusional? Seriously....how do you keep a balance of positive thinking while being able to honestly regard how you swim and what needs to change/improve? What do you guys do? Is it good coaching, simply having a solid self esteem in the first place....?? Is it simply that people carry their low self esteem into the water...if so, how do you overcome that...? Thoughts?? What in the world is sports psychology anyway?