Happy Birthday! Go out. Have fun. Get laid. Have some drinks.
*puts on white coat*
When I was in medical school, a 21yo gentleman who was celebrating his 21st birthday decided to take 21 shots of hard alcohol. He died. I saw them bring him in.
You will be permitted to legally drink every day for the rest of your life. You don't need to do it all tonight. And PLEASE put your cab fare in a separate pocket and make sure that you use it to get yourself home safe.
"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."