Mentoring relationships can seemingly go on forever if there isn't a discipline of checking in against some objectives. They can fizzle out or become more like chats and that's not the lasting impression either of you would want to leave. 

I've noticed that I sometimes censor myself, which means I don't say what I'm really thinking. And I expect I'm not the only one doing this. What are you not saying? At work, home or with friends?
It’s pretty tiring being radar-on all the time. Why not let some of the real you out?