Trust

Why is it that when we have been hurt, we can rebound and get our emotions back in check, however, we have a hard time trusting again? I have been truly hurt from experiences with past relationships. I was pretty much kicked over and over like a little puppy until I found myself cowering under a table. Now I wasn't really under the table; with my old (haha) body, that might be hard to get out from under, but in a sense I was. I was belittled and made to feel like nothing. I was cheated on which made me feel like I was not good enough. That was over a year and a half ago, and still I feel the remnants of it now. Although I am a strong person now, and feel it's because of what happened, I feel I am lacking. Especially in the trust department. Often times I read into things because I don't want to get hurt again. I tend to question who I am and whether I AM good enough. I just have a hard time with this sometimes, and it pains me inside. I just find myself worried of being abandoned, as I have talked about before, and worried of feeling pain again. So why is it that trust is the hardest thing to get back? Why can we get over many things, but have trouble fully trusting again? Why, WHY, WHY??