It is your mind. Use it or lose it. Vigorous older people are like this. Sitting in a chair watching TV every night is for those who do not want to use their mind. It is a fact that people who interact with friends, family and the community seem to live longer and better.
Sexual interaction is a normal human instinct and has no outer age limit.
Maintain sexual vigor as you feel is right for you. Finally, if you find that you are staying by yourself and losing interest in relationships and things you previously enjoyed, you may have depression. Discuss this openly with your physician. There is a great deal that can be done about depression at any age. Life has many frustrations and it is normal to become angry once in awhile.