[Breaking things only helps half the time, even if it's the first thing that comes to mind. He does at least have a collection of various things procured just for that purpose these days, so Hux can't complain as much about him wasting resources anymore. That's the thought, anyway.

He only briefly thinks of the time he tried very hard to break himself before moving onto something more practical.]

Anything physical that requires all of your focus and energy. Something that challenges you. It doesn't have to put you in mortal danger.