hanging out with friends but didnt invite you?

I feel bad of course if they did so..I feel sad really sad.. But just thinking positively, maybe they want give you some surprise, because this happen often in my case

i don't go to some one else place if i was not invited. i hate to be in a situation where they don't expect my presence or if they will not happy with my presence. cause i don't want or like to force myself to some one or any one that does not want me to be in their group.

This is a very critical one, though it never happen to me because most of the time we are a group of ten or twelve and if ever one or two is not present it means they are either ill or they have somewhere to go with families. If I were in this situation I would feel as if I am no part of the group because they did not think it is important to invite me so I would also keep my distance from them.