There's this myth that as one grows older one can now relax and do very little physical exercise. Well let me tell you as a 74 year old that is only a myth. To stay physically and mentally vital exercise is more important than when you were in your 30's or 40's.
I'm not talking about running marathon's or climbing Mt. Everest what I'm suggesting is minimum of one hour a day of some sort of exercise like a brisk walk, some jogging, stretching, swimming, hiking, biking or weights. Consistently doing a combination of theses different exercises will make a difference in your golf, tennis or whatever sport you play because it will improve your endurance and strength. Travel will be easier, you'll have more restful sleep and most importantly experience a sense of vitality.
The best medicine for your health as you age is exercise!!!
Keep it Simple, Consistent and Fun.