I hope you are safe. I know you are not feeling serious about it, but if it has such a strong presence in your mind, please consider seeking some medical help. You shouldn't have to feel this way.

Often when I have a great time with friends, I have a major mood crash right after. What was genuine at the time seems fake an retrospect. I feel like I was just putting on a show to fit in, I didn't truly connect. I feel like an outsider. It does often give me suicidal thoughts. I expect it now, so I just try to hunker down, distract myself, and ride it out. It usually does pass within a day or so.