Cultivate a work/life balance. You don't want "she worked really hard" to be the only thing people will say about you when you die.
Especially when you are young, don't close any doors until you are absolutely sure about where you are going. As an example,don't drop taking maths because it's hard. Persistence pays off, and you just might need that math course for your dream job.
As far as you can, try and be on good terms with people, even if they are not your type. Making enemies or putting people down just might create barriers for you in the future. I don't mean you have to love everyone, just stay on good terms.
Keep your friends close and your enemies closer.
Try hard to grow your confidence in yourself. You can achieve much more than you think.
Get good at public speaking. It can really move your career and reputation forward.
Don't compromise your morals and ethical standards. Ever. Nothing good will come of that.
Take care of yourself and your loved ones. Try not to create rifts and to be patient and tolerant. I was saddened by a recent thread about words describing mothers. So many were negative. No one is perfect. Not even you. Find a way back from disagreements and hurtful words.
Never go to sleep on your anger.