Finally, have your fun now. Five years is a long time when you are 23 years old. By the end of graduate school, you will be older, slower, and possibly married and/or a parent. So if you always wanted to walk across Nepal, do it now. Also, do not go to a high-powered lab that you hate assuming that this will promise you long-term happiness. Deferred gratification has its limits. Do something that you have passion for, work in a lab you like, in a place you like, before life starts throwing its many curve balls. Your career will mostly take care of itself, but you can’t get your youth back.
Even though the advice is written with the lab student in mind, I believe that the advice can easily be applied to everyone’s life.