The writer of this Psalm desperately wanted God to show His strength through him, an old man. He wanted everyone to know God’s power. As we grow old, we can still show God’s strength. As we become weaker, we can proclaim how strong He is. Do not lose heart as you grow old. The retired missionary now goes door to door to preach even though he’s walking slowly. The woman who started doing jail ministry long ago is often decades later faithfully visiting the jail. Whatever God is calling you to, God is greater than your age, Amen.
https://www.gotquestions.org/David-and-Abishag.html
And we pray:
Lord, as I grow old, let me still serve You faithfully. When I’m weak, help me to show others Your strength. Through wrinkles, let others see the joy on my face that comes only from You. Even if I’m moving slowly, let me still move for You. I will gladly do Your will until my last breath. If I’m on this Earth, You have me here for a reason. I will continue to live for You. In Jesus’ name. Amen.