The potential consequences that I can think of are: health-related (if you aren't properly using protection), being a "party girl" for the wrong reasons, and affecting your reputation/what people think of you.

Personally for me, none of these consequences are really relevant. I am very well versed in sex ed from school and the internet and know exactly how to use protection, how often to get tested, etc. I personally enjoy casual hook-ups and am not particularly interested in a more serious relationship right now (you shouldn't really engage in casual sex for any reason other than you want to have casual sex). I also don't really care what other people think of me in terms of reputation and am in a social crowd where no one really cares anyways because everyone is doing it.

I will say though that when I was younger, I was a lot less emotionally mature than I am now as an upperclassman. Hooking up back then was really different because I was pretty naive and had casual sex for the wrong reasons (because I thought it would lead to a relationship, because I thought it would help me get over a breakup, etc.) whereas now I mostly do it because it's fun and I don't foresee myself entering a steady relationship anyways when I'm graduating in a semester. My experiences back then definitely had a lot more negative effects on my happiness than my experiences now.