I got back into windsurfing in 2002. I realised immediatly I'd have to work on my fitness. From then I worked on my strength and fitness and have since enjoyed being able to sail for long sessions whenever conditions were right (plus I had a job where I could leave if it was windy). 6 months ago I went back to being self employed (so I could windsurf more??) and haven't had the time or the energy to go to the gym or ride my bike, I am too busy swinging a hammer, climbing ladders, digging post holes and a host of other ball busting tasks!.
While I was out sailing the other day I noticed, after continuous sailing for a couple of hours, that I was sailing effortlessly!! (and not because my skill had improved). I'm 50yo this July and never thought I'd "toughen up" again but I believe now that if you want to stay out on the water when it does blow, build your missus a limestone wall or dig up your back lawn with a spade!