Why do people keep disappointing me?

It seems like everyone lets me down, and I don't have outrageous of expectations. I would just like to be offered the same courtesy that I offer them: promptly returning phone calls, emails etc. I just found out that the girl who was my maid of honor (and I was hers too) was in town again with her family and never bothered calling since she was too busy with her other friends. I guess not seeing her is better than what she usually does: calls on their way out of town at some ungodly hour in the morning and expects my husband and I to drive across the city to meet them for a grand total of 10 minutes before they have to rush off, and we have done this. Anyway, I'm tired of everyone. It's better just being alone and having no expectations of anyone so you're not disappointed!