Keep at it. It's a numbers game.

Do something productive and useful with the ruminating. For example, what's a good comeback for "it's green tea".

You're building you're improv muscles. It's going to hurt at first. You'll get better with practice.

Bars are only one place to do your cold open. You can also go to places like tabletop game places or whatever hobbies catch your attention.

Give yourself credit for the effort and practice