#1 See your doctor and ask this question:
What can I do to extend my life expectancy? Follow your doctor's recommendations to the letter. Normally diet and exercise and maintaining a health BMI. Your doctor may give you a handout on how much exercise and what to eat and what to avoid. However, a lot of people ignore these recommendations. If you are overweight then set up goals. If you are not, then maintain your weight and eat a healthy diet.
#2: Next time you see your dentist, then ask this question:
What can I do to prevent gum disease? I did...and she recommend brushing your teeth with an electric toothbrush for 4 minutes! Most people stop after one minute of brushing so she suggested listening to music since a typical song last about 2 minutes 30 seconds. If you stop before the song ends, then you may have gum disease in the future.
#3: Have lunch with your co-workers and family and friends.
Your job was a source of stimulation and depression. The depression part is now gone but you should look for new ways of stimulation such as travel, hobbies, volunteer work, teaching, tutoring, reaching out to your neighbors since you have more time, more family time, etc In other words, use your brain. Use it or lose it! Focus on making new friends in retirement.