The big breakthrough for me was when I decided to start biking to work a couple of days a week. It's a 12 mile ride (one way) so the days I ride I get a pretty good workout in. My goal is to eventually reach a point where I'm doing that 3 days a week pretty consistently. That'll put me right around 75 miles a week, plus any other random riding I do.
Next year, after my shoulder is healed, I'll start backing with mountain biking and MTB racing again. I did one 6 hour MTB endurance race this year, but missed the rest of the season due to the shoulder injury.
If your posture is out of balance it might be a little harder to keep an exercise routine if your body doesn't feel right.
http://breakingmuscle.com/brazilian-jiu-jitsu/it-s-all-in-th...
https://www.defrancostraining.com/joe-ds-qlimber-11q-flexibi...
https://www.youtube.com/watch?v=3B-3Khbht5s
I'm in really good shape but if I don't stay stretched out and limber all of that goes out the window. I would say a good start to staying fit is minimizing the determent that siting does on the body.
Not exactly rocket science.
Not a great analogy, really.
Don't eat junk food too.