Even in sickness and infirmity we have dignity and worth. Some fears arise from the loss of a feeling of self-worth that accompanies loss of control over our lives. Our worth doesn't change with our circumstances. Our worth is the divine image in us, however imperfectly we may think we reflect God.
As believers our special worth and meaning is in the grace and love of the heart of Jesus. That doesn't change over the years though we do. Isaiah said, in the name of his people: “'The Lord has forsaken me; my Lord has forgotten me.' Can a mother forget her infant, be without tenderness for the child of her womb? Even though she forget, I will never forget you” (Is 49).
The Father sees Jesus in each of us. During Jesus' hours of powerlessness on the Cross he was no less the Son of God. In our infirmities we are no less God's sons and daughters.
When I am discouraged, Lord, remind me of the constancy of your love. Tell my heart that you love me early and late, well or sick. Then I will remain constant in my resolve to follow your lead.