"They also serve who only stand and wait."
This last line of the poem "On His Blindness" by John Milton relates to a person exercising patience and faith despite their circumstances. The person in this poem feels they are unworthy and useless to God. Their affliction- blindness - has hampered their ability to perform acts and deeds as they once did.
However, Patience lets this person know that in their affliction they can still serve God. In their affliction, God's great power becomes evident. God does not need the works of men or women. When we exercise humble acceptance of our circumstances and rely on God to sustain us, we inevitably become stronger - in the inward man - and allow God to work His pleasure in us.