Is he covering something up? how can you determine by just looking in his eyes?

I have a friend who's been to so many tragic moments that he has, I think, become cynical. Although he generally is a happy person I think it's just a mask. I asked him directly if he's happy w/ his life and he said yes but he doesn't maintain eye contact while doing this. He said that he really has a hard time making eye contact. Do you think he's trying to hide his real feelings that maybe he really hasn't overcome his bitter moments?