If you're stressing out over things with your real "friends", you should probably rethink some things. the real hard part is letting that other person know you don't want to be friends with them, because than it just makes more awkward for them.
Being Happy is not just a feeling. It's a skill. Find the positives about yourself, your body & the people around you. Take a moment to fully appreciate those positive things. I take time every day to focus on the things I am grateful for.