Why do I become sad when i am on facebook?

[J So]

Hah, I felt this way too.
I think you just feel like you are inferior to them, but they just aren't any better than you, so don't feel inferior.
Instead take things like this with a grain of salt, at the end, parties and fulfillment aren't intrinsically linked. You can be fulfilled and happy doing things you like, if you feel like parties are essential to this than go make yourself some opportunities to go party.