Must is different.
Must is who we are, what we believe, and what we do when we are along with our truest, most authentic self. It's that which calls to us most deeply. It's our convictions, our passions, our deepest held urges and desires - unavoidable, undeniable, and inexplicable. Unlike Should, Must doesn't accept compromises.
...Choosing Must is the greatest thing we can do with our lives.