Ok. So, you’re minding your own business and going through your warmup for the morning when all of a sudden, you see a crack in your instrument (this just happened to me). It’s fixable, but you need to send your instrument out for repairs. This is always the part about cracks that I worry about. Thankfully, I have a repair tech that I trust will do a good job, so my worries aren’t necessarily “Can this be fixed.” Rather, my worries are “This will cost x amount” or more commonly “My instrument is going to be gone for x days/weeks. How am I going to practice?!” Believe it or not, there are ways to continue practicing without your instrument and you may even find they are so effective that when you get the instrument back, you will be compelled to keep working on these techniques!
Exercise the corners of your mouth - This is a great exercise for keeping your embouchure strong or simply building strength in your embouchure. Often when I am away from my instrument for an extended period of time I go through this exercise to stay in shape. Michael Lowenstern has a great video on it here: https://www.youtube.com/watch?v=B4d2gpRysZY
Ever hear of air-guitar? Yeah, do that, but for clarinet… - No, I’m serious. Many might just stick to score study and listening and while this may be beneficial, actually fingering along to a piece without the instrument helps with finger memory. It also helps with better hearing what musical ideas you want to express by taking the instrument away for a little while, which can often distract us.
Finger independence exercise - Take your hands and form them the way you would when playing. Now, touch your fingertips together and work on moving them slowly. This helps with building finger independence and coordination without the instrument.
Finally, if you’re able to, don’t be afraid to take a break - It doesn’t have to be a long one, but if you can, take some time away from the instrument to breathe and destress. Personally, I like to devote a little time every day to doing breathing exercises. You may find that you feel more inspired to get back to playing once your instrument is back from the shop!