“Regularly play and learn new sports”, functional fitness, general physical preparedness, or the idea with in the CrossFit methodology that it will prepare you for random things that life can throw at you. Just considering exercise in general the reason most people do it is to get in better shape, but why are they wanting to be in better shape? I think exercise often gets turned into an excuse to be lazy in the other aspects of your day. Even worse it becomes something that you let take priority over other things because you don’t see them as exercise as you have come to define it.
Taking the time to try new activities could lead to finding a new passion for something. You’ll probably find that you even get more fatigued, or even sore, than you were expecting. Go rock climbing and see how sore your forearms are for the next week even though you do pull ups all the time. Try a hike on a nice afternoon and you may have an interesting time going up and down steps the next day. It’s common to think that whatever you do for exercise is the best thing, but there’s a reason there’s so many different things. It also starts to just become part of our routine and to not even think of it a lot at some point. Doing something different becomes an experience though, and those create memories. You probably won’t remember what workout you did today by next week, but taking up your buddy on that offer to try his Jiu Jitsu class will come up in conversations a year from now.
If you’re someone who runs every morning there’s no reason to not go for a hike when a friend asks out of the blue. Having already ran that day, or planning to go for a run at that time, should not be a reason you don’t go. Being afraid it’ll make you tired and affect your next workout should not be a concern. Unless you’re a professional athlete the reason you’re exercising is so you can do things like that! Hiking, skiing, rock climbing, going for a bike ride, or walking the dog. There’s so many things that you have the opportunity to do because you exercise, and exercise shouldn’t get in the way of those opportunities.