In theater, in improv, you learn the power of "yes," and "yes, but.." You learn that "yes" is needed to keep the game moving forward, and that every "yes" can lead to discoveries, unlikely adventures, and satisfying conclusions.
"Yes," can also can propel you into lots of jams and unfortunate circumstances. Sometimes you can build prisons of the mind and soul with the word "yes."
In life (which is basically just a very long-form improv), you also learn the power of "no." No is a very useful tool. It's a way of cutting and pruning away things in your life. It is a negation, and a blunt knife that should be used sparingly and wisely. But "no" can save you lots of pain and heartache and keep you out of ridiculous and time-wasting detours.
The trick of course, is to balance the yes/no quotient in our lives. There is no easy formula or operator's manual on the shelf to help you out. You are left to rely on your own wits and no-how. And you rely on experience, intuition and gut instinct. Not exactly the most reliable tools.
So yes/no, it's another art, an art that we practice and kind learn as we go...