Well basically, I keep myself fit and healthy by eating a good diet, I don't eat a lot and don't eat between meals. Stick to quality foods , plenty of fruit , veg , muesli , and natural yogurt. Not stuff with added fat and sugar. Don't smoke, don't drink excessively, a glass of wine is ok with meals. (((( Don't breathe, just kidding))) Rarely eat cakes and puddings. Drink plenty of water. Outdoor exercise. Keep sitting at a computer to an hour or two. Keep mind and body fit. Play piano or whatever is your choice instrument. Above all, be happy!
Easier said than done though. Do all that and you might not get a lot done. Get a lot done and you might start wearing down.