I was like this from ages 12-18, perhaps? It started because quite a few people actually were mean to me, but my brain incorrectly extrapolated and assumed everyone was. The beginning of the end was when I started to do something that I had defined as the province of the liked-people (in this case, dating), though it took about two years to purge the habit.

Perhaps there is something you are similarly defining to imply likedness, and you can do that thing.