I went crazy over boxing a few years back and got to the point where I was going to fly to Oz to have my first pro fight, my passport got through two days after the fight, life got busy so I canned it. If anything I got mental toughness out of it. I was trying out for the army too at the time, and we ended up with an ex SAS guy that would take us through our paces which made boxing fitness look like blobbing on the couch, what really changed my life was the mental drive. It gave me a huge expansion on my capacity to just keep on keeping on no matter what. Running stairs for a few hours, making sure the only reason you physically can't keep going is because you can't, not because you don't want to...
I miss it, been thinking about getting back into it but I got fat and lazy after boxing. Canned the cardio, pumped weights, bulked about 5 kg's and got 10kg's chubbier when I moved to South Africa. Went from 75 to 89 in about 6 months, part of that was newly married life though.
In conclusion, it's awesome. Do it, but only if you're committed (Spending your own time kind of commited, every day, not just busting your ass because a coach is saying so). I sparred a lot of people who were boxing because of how they thought it made them look, and it never did them well... I think it humbles you too, and I haven't met many people who don't need that. Especially me lol.
I think my mindset affects my drumming more than the physical ability I get out of something, so that's what I got anyways.