I come up with insults and comebacks for the people closest in my life just in case they ever hurt me.
Why would you feel the need to do have comebacks ready?
I like to be prepared.
We all like to look witty, but it's bad to have petty revenge already thought out against your friends. If you like your friends, you should be planning good things for them instead.
I just really like having options.
It seems quite strange to have a plan for hypothetical situations. If you have trust issues you can talk with the people close to you about your insecurities.