I used to be good at this! (Or at least I used to consider myself good at this...and I still can be quite good at it in circumstances when I have to, or when the person concerned is already someone I'm close friends with or respect.) Maybe the problem is that I'm such an emotional sponge that unless I make sure I hang out with people who have a variety of opinions, one side is going to start winning out and the emotional weights I attach to my beliefs will get messed up.