Not just for COVID times. My advice for a functional life, for as long as one is given by God or nature, is to workout 5-6 days/week, stay fit and trim (the latter being mainly nutritional). Don't abuse substances. Have a good sex life and social life. Do things, and take on new challenges whether mental or physical.
I will never advise anyone about what to eat. Westerners are over-nutritioned. If overweight, eat less (especially carbs) and, if underweight, eat a bit more of everything. Simple. If you lift heavy, get some extra protein because it won't hurt.
Get a physical exam, mammogram, PSA, and cardio stress test, however often your doctor suggests. The Maggie's Fitness for Life exercise regime requires more structure and discipline than very many are willing to do, but we recommend it anyway - 2 days of HIIT cardio, 2 days of calisthenics, and 2 days of heavy weights. It will not extend your life, but could make it more functional and lively.
If you hit 80-90 years old, do whatever you want. You made it to the finish line.