The first thing to address when thinking about a healthy mind has to be the biological brain-as-blob-of-meat issue. Wait, don't skip this one!
It may seem like you've already heard about how it's important to keep your body healthy. And it is. But not just for the nebulous goal of "health and long life". It's impossible for your brain to function at its peak if your body is poorly maintained. You can actually contract mental illness just by failing to take care of your body (Moy 2009). And not just dementia or anorexia nervosa.
If you're concerned about maintaining your mental health, or if you've struggled with depression or anxiety and you worried that you might relapse, you can't afford to dismiss your physical health. I'll talk more about what that exactly means. Yes, I actually talk to myself to help me write. Shut up, it works.
This makes sense, if you think about it. Your brain is an organ, so just like your heart or lungs, it's affected by obesity, high cholesterol, thyroid problems, vitamin and mineral deficiency, and myriad other conditions. The brain is powered by nutrients in the blood, which come from everything you consume, like food, beverage, drugs, air particles, and chemicals. If you don't take care of the brain's needs for nutrients and oxygen, it can't possibly serve you properly. It would be like giving a race horse nothing but corn husks and dirt and then wondering why he doesn't keep up with his peers. Your brain only gets what you decide to give it. You have to actively choose to give it the best you can, and your brain will serve you well for years to come.
I'm fixing to (my mom is from Oklahoma, where that phrase is common) give you some ideas on this in later posts. The main one I want to emphasize for now is regular check-ups with your doctor. And while I'm at it, nothing on this blog should be considered as medical advice, because I'm not a doctor and I don't want to get sued. And I don't have anything worth suing over, except my wonderful family.
But you should go see your actual doctor. He/she can do all kinds of helpful things, like checking your blood pressure and BMI, monitoring your prescriptions, answering questions about any symptoms you have (you want to get that rash looked at), and telling you about other tests you should have regularly, like mammograms, prostate screening, and PAP tests. Although these things don't seem directly linked to your mental health, they absolutely are. That fatigue you're feeling could be a blood chemistry problem, and the anxiety might be caused by excessive caffeine or sugar. You could get the mental health symptoms taken care of as easily as a single doctor visit. So call your PCP (primary care physician, not angel dust. More about drug use later)!
Moy, M. L. et al. Multivariate models of determinants of health-related quality of life in severe chronic obstructive pulmonary disease. The Journal of Rehabilitation Research and Development, Vol. 46, 2009, pp. 643-54