Hey, I am no expert.

First is to get a complete physical, know what you are dealing with. What are your limitations and constraints, what are you requirements? This impacts diet and exercise.

Eat well. I tend to stay away from processed foods as much as possible, as much because I like fresh more as anything else. The body needs nutrients, give your body what it needs. Just don't give it more than it needs. Diet will need to be tailored to the individual's needs and restrictions. As we get older, we need less food, but more nutrition.

Exercise. Again, your particular circumstances and health will drive how you exercise. I will venture to say that you should get as much intensity as you can, within your health limitations. I work for both strength and endurance, pushing hard for extended periods. I try to work my entire body. This has been difficult due to my somewhat numerous injuries, which place some significant limitations on what I can do. At one point, I lost the use of my legs, and was told I would end up in a wheelchair. That was 13 years ago, and I am still walking, but I do not run. Too much impact on the spine. I walk and use machines to try to increase my endurance through increased intensity of the exercise. Everyone has to understand themselves and their own unique circumstances, and adapt an exercise program accordingly. I will say that you should get as much intensity as you can.

Mental Health. The references I posted earlier are a good beginning. Making accurate causal attributions, developing a mindset that can grow, is important. The brain is an amazing thing, and it needs to be worked like a muscle. Injuries and problems can be fixed to a larger extent than we believed 10 or 20 years ago. Even problems with anxiety and depression can be helped. You need to want to do it though. You have to make the effort. Constant learning is a great way to exercise the brain, especially as we get older. Exposure to new experiences and new learning can help to stave off some or the problems we have as we get older. I do recommend meditation. I was actually taught as part of a military program a long time ago that he'd the intent to see how the mind can overcome physical limitations. It worked for that to some extent, but it is a great way to deal with stress and develop mindfulness. Mindfulness is simply being more aware of everything, inside and out. And understanding what it is you are aware of. Emotions, like anxiety, can be wrongly attributed. An understanding of yourself and an awareness of what you are feeling and what is going on around you can avoid making such mistakes. If you are up to it, I recommend at least a basic level of understanding of how the brain functions. That alone can help you understand what is really going on when you feel something, especially something that feels bad. I know that it sounds kind of squishy, but there is a lot of good scientific research to support this, and they are learning more all the time.