Getting waitlisted at colleges is nothing to be sad about - you were one of the top applicants to the school! Depending on how many students accept, you still have a good chance of getting in.
Remember that amongst the waitlist candidates, you can still stand out. After accepting your spot on the waitlist, it never hurts to update the admissions officers about what you’ve been doing since you submitted your application.
You want to show them that you haven’t just checked out and taken it easy senior year, but are still motivated to keep excelling. Often you can just send them an email reaffirming your interest in the university, and jotting a few updates. Sometimes a creative approach can work here as well. I knew a student who once created a kinetic typography music video and wrote a song describing why he’d be a good fit for the college and ended up getting in!
Note that it’s important to not go overboard with this. The admissions officers don’t want an email from you every other day and another ten recommendation letters. If you’re unsure, you can probably contact the admissions office or a local admissions officer (if you have one) and ask about the best way to send an update.
At the same time, you should still move forward with your next best choice, since often the deadline for accepting an offer is before waitlist results will be released. If you get in, great! If not, remember that it is up to you to shape your university experience - you can make it as amazing and productive as you like just by working hard and making good use of the resources provided.