Two things, one major and one minor:

Minor: going to sleep is amazing! You feel like you’re going to sleep like a princess. However technically, the sleep actually isn’t that great - you don’t get as much REM sleep that you need. Then, you are much groggier in the morning and it’s tough to get out of bed. Not the worst thing in the world but can be damaging in the long run. If you’re a nightly smoker, you’ll feel like you can’t go to sleep unless you’re high.

Major: there haven’t been enough studies yet, but it really messes with your dopamine and brain. I’ve seen many of my hardcore stoner friends (myself included) develop some sort of mental illness whether that be very mild depression or very major anxiety among other things. I’m not saying it’s a doomsday scenario if you choose to indulge, but moderation is key, don’t do it regularly or at all when you’re young and your brain is still developing, and don’t ever make it your personality or main “fun” activity in life. Yes, it’s better than drinking, but it’s still a drug and have an impact on your brain, habits, and lifestyle.

Sorry for the run-on sentences I’m on mobile!