Sounds like me
I guess it's because we're scared of taking risks. I know a couple of aggresive players, they dare to raise almost any hand and know when to fold'em as well.
Then again, it's not about the cards.
In fact, the other day we were playing a 6 man SNG at my place (10 euro buy-in, 1 rebuy) when I got raised after hitting a J on the flop with my AJ. The guy raised my bet and I had few chips left, so I moved all in. He had paired his hand as well and based his move on a read. Bad read... but bad beat for me as well as he hit his set fours on the river.
Cheers,
Giorgio