Saying yes when you know you should be saying no

Do you say yes to things you know aren't in your best interest because you're worried about what others will think if you say no?

You only have so much time in a day...in your life. Why in the world would you want to be throwing that time away? If you say yes to something, does it evolve you? Have impact? Make a difference in someone's life? Your organization? Unless you can say yes to some of those questions, it's time to redefine.