Way back when I was a teenager, I had braces for about two years to fix the Bugs Bunny teeth I had back then. Having braces is very uncomfortable and a huge pain in the ass, but it fixed my teeth, making my smile perfect.
When the braces finally came off, my orthodontist at the time gave me a thing to wear at night called a positioner. “As long as you wear that every night when you go to sleep,” he said, “your teeth will stay in place and will look perfect forever.”
Being the dumbass teenager I was, I wore the thing probably three times and then threw it away. Like all teenagers, I Knew Everything™, so I figured that it would be fine.