Colin, as you know as you get older, and you are certainly getting older, you will have to do more and more of that exercise thing. Based on what you said above you already know what to do - it is just doing it.
The most important thing would be to do things that are physical that you enjoy doing like the martial arts things, skiing, etc. Good that you are on the right path. I was thinking about doing the martial arts thing myself... i have a place that I can walk to from my house.