Newton's First Law of Motion. Keep moving, stay moving. Keep eating healthy and exercising, stay healthy and fit. Keep learning, stay sharp and knowledgeable.

There are more life frictions as we age that dissuade us from continually learning. If you realize this and work against it, there is no way someone significantly younger than you can realistically be a better fit for a job. They may have knowledge, but you'll have that and decades more experience and wisdom.