Getting braces is tough, especially when you play a wind instrument.
3 bits of advice...
1) first be patient with yourself. Your mouth muscles need to re learn where to go because they are in a slightly different place. There may be discomfort, but take a rest when necessary. You will rebuild your embouchure little by little, just like you did the first time, only it will definitely go quicker!
2) second, if you play a brass instrument, you make ask your orthodontist about using wax on your braces so they won't be so abrasive on your lips.
3) lastly, PLEASE DON'T GET BRACES RIGHT BEFORE A CONCERT! Students work so long and hard to prepare for their concert performance and suddenly getting braces right before the big day could be an unbearable challenge.
Remember...this is TEMPORARY. Millions of great musicians have gone through this, and you can too!
Here are a few great articles on the subject: