I can relate to this. I often get frustrated before meeting someone, even if it's a good friend of mine. I am an introvert and I enjoy time alone, but I can also have fun socializing. (Though when I'm out with friends I often come home earlier than the rest).
I've noticed that when I feel frustrated, "not in the mood to go out" etc. it's usually not as bad once that I actually do it. Like, the idea of it is always more difficult than the reality. I try to force myself to not to cancel the plans I have with other people.