If you're over there trying your best to have fun, you aren't having fun. Having fun is letting yourself go and jump around, and being yourself. Not adhering to a standard. Be around other people who are having fun with you, and that let yourself go.
High school may never end, but that does not mean that life should be a dull adventure. Life is amazing, and life is a treat. It's a blessing, not a curse.
Follow life, and have hope, and let yourself have fun. Do not force yourself to have fun. Don't force yourself to have fun with other people either. Have fun. Realistically and practically speaking too.