I'm lost... what do I do now? Part 8 (Improvising)
Put the jam track on that you've been practicing your instrumental with and improvise. Work your Hole Changes (Accompaniment Study 3), Chorus Forms (Improvising Study 1), Soloing Themes (Improvising Study 7) and general jamming with a goal of becoming very familiar with the groove of the song you're playing. This way, if you unintentionally deviate from your prearranged instrumental, you won't freak out.
Now grab your list of first chorus licks (see "I'm lost... what do I do now? Part 5 - Memorization") and play your instrumental one time through with the jam track to warm up. Now put your jam track on and play the first chorus lick and then purposely deviate from prearranged chorus and improvise. When the turnaround comes, try to remember the lick for the upcoming chorus (if you can't remember, look at your sheet) and then start your next chorus with the correct lick, as if you never got off. For this new chorus, again, somewhere in there intentionally mess up so that you can practice getting back on for the following chorus.
The saying, "Luck favors the prepared." is exactly what we're going for here. If you practice what to do when you get off, let's do it, so that you can walk up to the bandstand with confidence that you've done what you can to be prepared, and now it's time to have fun!