I'd also like to point out that my disappointment is directly related to the strength/attachment of my relationship with the person. I think I'm pretty good at not expecting things from most people, in part because I don't feel entitled to, although there is also guilt associated with those I have a strong emotional connection with. So, the guilt is always there and the pain increases in proportion to the emotional bond.

I assume this is all very obvious and applies to everyone, though.