Life.
Opportunities to train come and go. People move, people lose touch, people grow beyond that which the current sifu is able to teach. Some are referrals, some are merely doing it because they wish to learn another's POV.
Life.
"I don't know if anyone is known with the art of "sitting on your couch" here, but in my eyes it is also to be a martial art.
It is the art of avoiding dangerous situations. It helps you to avoid a dangerous situation by not actually being there. So lets say there is a dangerous situation going on somewhere other than your couch. You are safely seated on your couch so you have in a nutshell "difused" the situation."