Truth is, probably never!
When you learn to play music, you gradually get more skills, more musicality, more technique BUT you never really are at the level you'd like to ideally be.
This is how you grow. You challenge yourself so you grow.
So, when you get a big opportunity that you can do but maybe feel nervous about, if you relatively have time to prep, take it, do your best and learn from it. This is how you grow.
What do you think?
Are we ever ready?