Aggression
You need a new outlet for your aggression.
Watari's comment was meant to spare the shredder and the limited paper for sacrifice.
Kazuma suggested boxing; Tatsumi scoffed initially before his curiosity won out. Compared to Kurosaki's iaido, it was violent and ugly… and perfect. A few tentative jabs quickly turned into an hour spent abusing the punching bag every morning.
The downside: he had to buy three new suit jackets, shoulders too broad for the old ones.
The upside: accounting refunds came quickly, Kazuma gained a sparring partner, and Watari a spring in his step…when he could walk again.