Depends what you mean by nh!! To me nh means asking 'why' instead of 'how do I...'. As in 'why is my horse napping' not 'how do I stop my horse napping'.
Coz to me nh means understanding how the horse is seeing the situation.
And to be able to do that you need some understanding of how horses think, feel & behave, awareness of behavioural principles and also some knowlege of YOUR horse and how he/she reacts. Plus some ability to read a horse's moment to moment communication.
Once you understand the 'why' you can figure out the 'how to'....as different approaches might be useful/useless/harmful depending on the 'why'.