Jonathan Hi !!
It is a nice post and definitely has deep insight.. what i felt after I visualized situations in my life is that for many situations I can adopt your four step suggested method and get away with a happier and lighter mind.. But there are situations when if you ignore unwanted commitments you may be considered as a less social form of human being or you even might get into the "List Of People I hate" for many people around you... Now I would suggest an addition to theory that when somethin like what i said happens you must ask one more question to yourself " Do I care in which list people keep me ? "..

Shanel's Idea of "May Be" is somewhat more practical I believe ..
But believe me I have always wanted to say NO to things I don't want to do.. But Have failed more than 50 percent of times .. And I believe most of us have failed too...