I have to constantly remind myself of this! Don Draper put it another way, "If you don't like what's being said, change the conversation."
So many of us get caught up in complaining about the day-to-day, our jobs, our relationships, etc. but yet we don't do anything about it.
I think it starts with being grounded and in-tune with yourself. Are you happy? If you're not, why not? What can you do to change it? I try to do this daily. There's ALWAYS something you can do to help you change- or at least get through- your current situation.