Stay true to yourself and never let anyone change you.
The only limits you have are the ones you set for yourself.
你必须度过一些糟糕的日子才能赢得人生中最美好的日子。
The only constant is change, continuing change, inevitable change, that is the dominant factor in society today. No sensible decision can be made any longer without taking into account not only the world as it is, but the world as it will be.