Try the open mic alone first. No friend to hide behind shows you exactly how brave you already are.

Company changes the test. With a friend beside you there is always somewhere to put the nerves, a shared look, a joke to break the tension, which is comfortable and quietly removes the thing you came to find out. Going alone leaves the fear with nowhere to go except through you.

If there is something you have been meaning to try, do one attempt without bringing anyone. Tell nobody beforehand if that helps. Whatever happens, you will walk out with an accurate reading of your own nerve instead of a borrowed one, and that reading tends to be better than expected.