Our God is so creative that He is able to take any available heart and make Himself known.
He is able to love through anyone who will let Him. He will use youthful energy or he will use the immobile elderly. It does not matter.
Give Him all that you are and all that you have. He will reveal Himself to and through you. The first commandment was not issued to the most mobile or the most intelligent. It was given to all.
Soldier of The Cross, the only limitations you have are those you think prevent you from being useful. The Lord does not see you that way. Otherwise, He would not ask that you take up The Cross daily.
Look up and move on!