Above, i agree with so much, parents included. You need to make sure your happy and not unhappy and depressed, and to hell with others its your life not theirs.
Dont dwell on the past, if you didnt do something or missed something its gone, and its a memory, better to use it as a learning experience for the future, than rerunning it over and over.
Listen to people who have had more experience in something, than thinking you know better.
One thing i taught myself early, every moment of everyday is a learning experience, dont ignore something that could be important to you later in life no matter how insignificant it may seem at the time or how stupid strangely enough it may save your life later on.
If someone is completely unselfish and wants to help you, accept it, if they just want to be nice and have no expectation of a return take what you can get, but its still nice, to do something nice whether they expect it or not. optional before anyone comments.
If something is annoying you, dont persist walk away, its just another form of stress which you dont need in your life, or if its something you can do something about, put your best pair of steel capped boots on and stomp on it till it stops annoying you.
Dont let the pressures of society to feel as though need to get married and have children, if you find a partner and you know it will make you happy and its mutual fine, but let it be your personal choice, same as children, your bringing human life into the world, just because you can doesnt mean you should, unless you know this is what you want, and that, that child is not a pet, dont look back on it later and think i shouldnt have done this, take it seriously.