No!
\ ˈnō

Seems children hear that word a lot, maybe adults as well. Children love using the word as much as possible to assert their independence and free will over as much of their world as possible. It’s natural and part of their normal development. But hearing NO often enough makes that world seem like a place that is not built for young children and one where they may become oppositional just to feel like they can control a situation Instead, try using alternatives to NO. Try using alternative phrases and opportunities to make positive choices such as: 

"I understand you want another cookie now and so do I. You can have an apple or a string cheese now and another cookie tomorrow. In fact, I will put that cookie into a baggie and save it for you so it will be waiting for you!"

This type of alternative does take longer and might feel difficult in the heat of an emotional moment (especially when a child is asserting themselves). And when we are emotional, frustrated, or at our wit's end, we may not feel like being so accommodating to our children (or spouses). But that little bit of investment now will pay you back in multiples over time as you sow good energy that will reap more good energy in your life and the world.