Why do things have to be so Black and White (pardon the pun)? Surely there's a gray area. Why can't you enjoy a little of both worlds? Be responsible for 40 hours a week, sleep for 56 (that provides 7 days of a full night's sleep) and you still have 112 hours to do whatever.
There's nothing wrong with having a good time but returning to "being basic" (whatever that means) when the time comes. I made it through undergrad with honors and partied almost every weekend (Friday and Saturday nights were for "getting it in", Sunday morning was for recovery, Sunday night... back to the books).
As others have said, there's a greater need for self reflection and understanding. WHY were you such a "free spirit"? You mentioned that your being a free spirit left you with hangovers. Could the drinking / partying have possibly been compensation for a deeper underlying issue?
And if you are "BASIC" make sure you've given yourself that title and not fallen prey to someone else's negative view of you. Learn to love your quirks, because until you truly accept yourself, no one else will. Chameleons get tired very quickly.