Stop, reflect and remove yourself from the situation. I try, extremely hard, to be objective about the things going on in my life. Once my crazy thoughts settle on any frustrating issue, or my excitement cools on the great happenings, I look at all sides and try to determine what is fact, fiction and where to go from there.
Great example: I'm a little fed up with a close friend of mine at the moment for only calling upon me when in need. Shoulder to cry on, fight with her boyfriend, ride to the airport, watch her dog while she's out of town. I've always prided myself on being the friend you could rely on, but I want to be included in the fun stuff, too.
I could get angry, yell at her and tell her I'm no doormat. Or, the more rational adult approach would be to understand that I have volunteered and been happy to help in the past. It gives me a sense of fulfillment to support and assist others. (Obviously, sharing my life lessons via blog is another pathway to helping).
Seeing the situation in this light gives me more compassion when dealing with her, because I'll be aware that she probably has no malicious intent.
My solution: simply tell her that I love helping, it makes me feel good about the friendship, but that I would really like to be included more for the festive stuff. Tell her I'd appreciate invites and offers that do not involve assisting her, but that are just about us connecting, bonding, or having fun together.
Anyway, that's now I learn the most from life's lessons. I make sure to consider every viewpoint I can think of and what the other person may have been thinking, feeling, motivated by when acting.