My mother once said never say "can't". Sometimes we think we cannot do the impossible. It's possible you can trust. You can take tiny steps with it by letting people in slowly. You can divulge little unimportant things first and then see if you can trust them with it.

Really it's a smart thing not to trust right away. We live in a dangerous world now a days and you are right not to be all trusting.

"Man's mind stretched to a new idea
never goes back to its original dimensions. "
Oliver Wendell Holmes