Some of the reasons I don’t like using the word ‘NO’ in training:
It doesn’t teach your pet what you’d like for him to do instead.
It can create apathy, fear, anxiety, aggression.
Your pet will associate you with that aversive consequence.
You may simply be teaching your pet not to do the behavior in front of you that you wish to stop.
It does nothing to foster a love of learning.
Instead of saying ‘NO’, practice finding those teaching moments when your pet is doing behaviors that you like…and tell him ‘YES.’