Is it possible to become more insightful, enhance one's people skills, and become better at knowing people? If so, how?

I am frustrated by my inability to give my girlfriend sound advice on a variety of life issues. It’s something she asks for that I seem unable to provide for her and is therefore one of the main constraints on our relationship. Prior to this relationship, I was involved with people who didn’t point out this deficiency so I have managed to move through life until my late 20’s without “fixing” the problem. I would like to be better at explaining why people do what they do, explaining to her when a fear is irrational or legitimate, etc. so that I can provide her with insight, but sometimes when she asks me questions I truly don’t know how to respond. Please help!