The emphasis should be on movement here. Too much, too hard exercise can actually be detrimental to your immune system. If you know someone who's training all the time, maybe you do it yourself. I'm sure you've noticed that it can make you more prone to infections, catching a cold, and so on. That's the body's way of saying, "we had too much, time for a break."
I'm a huge fan of high-intensity exercise but not every day for extended periods of time. Hours of crossfit training daily might not be ideal for your immunity. So the focus should instead be on lighter exercise and movement that is sustainable long term.
A good rule of thumb here is that if you feel energized after exercising, you're doing it right. If you're feeling drained and tired, you probably overdid it. Make sure to not do too many of those sessions every week, spread them out. Once in a while, it's great to exhaust yourself completely, but not all the time.
Most of your training should be generative, build your body and health up.
It will benefit your brain health and cognition to actually start moving in new and different ways.
Try to get more movement complexity in your day to day. Take up some new activities, look up new ways of moving and exercising your body on youtube or go to a class somewhere. Don't just limit yourself to repetitive movements like walking, jogging, cycling, or weight lifting.
I also wanna mention the importance of mobility and stretching. not always that fun to do, but it's very important to oil the machinery, especially as we grow older. Our joints stop lubricating themselves when we're around 30-35. After that, we need to move to get synovial fluid into the joints to keep them healthy. Stiff joints contribute to inflammation, which degrades your overall health. So just like sleep, this is something you need daily, and this is another reason why more complex movements are really beneficial, then you get mobility training as a byproduct, so to speak. And if you need another reason to move – remember that the body also has systems like the lymphatic system, that have no built-in pump but are dependant on breathing and movement for the circulation to work.
The last thing I wanna touch on is that the vast majority of people today, due to a sedentary lifestyle combined with standard gym/fitness training, have greatly underdeveloped backsides. It would really benefit most people to focus MUCH more on training the whole backside, legs, butt, and lower, mid and upper back. I can't go more in-depth on this here, but youtube is your friend.
If you want your body and mind to work in a healthy, productive state, and relatively pain-free until you're 80,90,100 years old, you better start taking care of it now. So think long term here.