Relationships are a must whatever your age.  Good friends increase longevity in seniors.  Positive thinking makes you feel good and will help you stay active.  If you can only hold one thought at at time, make sure it is positive. If living alone, get a roommate of like interests.  They can share the work load of a home, giving you more time to be out and about.

 Don't sit around - also exercise.  This will help with your strength, balance and flexibility.  This also helps you to enjoy life more and feel better.  Join an exercise class, ride a bike, swim or walk, or even get a pet.  They're company and keep you active and not sleeping all the time.  They need exercise so you will get yours.  Get out and around people.  Other ways to keep busy are to join a book club, go to the theater, walk in the park, become a mentor, have dinner parties, contact people you've lost touch with, spend more time with family and friends, get a hobby if you don't have one, travel, volunteer, be a companion, if bored, get a part-time job that you will enjoy and are able to handle.

Keep your mind active.  Take adult education classes, or learn other languages.  Take studies that offer self discovery and growth.  Increase and perfect your hobby.  Teach others your skills, and don't stay at home.  Have fun in retirement.