My kid usually wants to know how I make decisions and never settles for a single "no" or "because I said so". I can tell them "because I want you to find some other stuff to play with", which might result in complaining for a while. Saying "not hard" is definitely not true in many cases. It's doable, but it's still hard.
Whatever works for your family. The more you set the boundary though the better. I guess the ideal parenting method is to reinforce good choices and not reinforce bad ones.
The best trained dogs are those trained only by positive reinforcement so…