Let me say first of all that the advice so far given by contributors to this thread is all good and I would not disagree with any of it.
As an additional suggestion, however, if all else fails try having the odd hour or so with a different instructor. Try to find someone from a different background.
For example, if your present instructor is ex military, find a civilian; if your present instructor is a civilian look for someone from the military.
You may find that someone else might teach the things you find difficult in a different way that may help it 'click'.