My list:
Keep moving - you may be slower than you used to be, but do what you can.
Spend time in nature - walk in the park or woods, sit on a lakeshore and watch the sunset, walk in the rain or snow, plant and nurture a garden, a garden box or a houseplant.
Read widely, volunteer, take classes, travel if you can to be aware of the world we live in today.
Ask younger people about their lives without talking about how things "used to be", listen to their answers without judging. Gently share your experience if asked.
Try new things - foods, hobbies, different genres of books or different authors, haircut/hairstyle, well-fitted clothing with accessories (new, recycled from your closet or thrifted.)
Practice your religion, yoga, tai chi, meditation or other mindfulness.
Try not to talk about aches and pains, medications and surgeries - especially to people you just met.
Turn off the TV, walk away from the computer, put down your cell phone and DO something.
Smile and appreciate the world around you.

Off to shower an walk in my neighborhood.