This quote by Oliver Wendell Holmes is a funny way of expressing the concept that age is relative. It recommends that age is not a set number, however rather a subjective experience. It suggests that a person's age is determined by how they feel and how they perceive the world around them. It likewise suggests that age is not necessarily identified by the number of years one has actually lived, but rather by the experiences one has had and the knowledge one has gotten. This quote is a suggestion that age is not a constraint, however rather an opportunity to discover and grow. It motivates us to welcome our age and to maximize the time we have. It is a suggestion that age is not a barrier to living a full and significant life.
"Have regular hours for work and play; make each day both useful and pleasant, and prove that you understand the worth of time by employing it well. Then youth will be delightful, old age will bring few regrets, and life will become a beautiful success"