I think stretching daily is of huge benefit, as is some form of weight training to build and maintain muscle mass.
Look after your eyesight. Things become more difficult to see, both close to and in low light once past 40.
Keep up to date with technology. Not just phones but TVs, cars, audio/visual equipment, apps, on-line services (banking/investing/tax included).Dont be one of those people left behind thinking it's just a fad.
Try to keep working, even if just part time or volunteering.
Read the news from a range of outlets.
Keep up with or return to your interests and hobbies.
Keep learning. Future Learn/Udemy/University of the 3rd Age/Duo Lingo etc..
Eat well, little and often. Use supplements.