Acceptance

H. Siddons Mowbray "Gethsemane" (detail)

All humans aim at a perfect plenitude of being and happiness. Satisfaction comes with a sense of fullness, a sense of plenitude that does not require anything more, and is perfectly contented in itself, or in the enjoyment of its object. And nothing on this level of reality can give us access to this satisfaction, and it is only in transcendence. Thus, spiritual satisfaction  in God is a response to the human tendency toward insatiability and give us this sense of fulfillment, one that is bi-ghayri ḥisāb, or without measure, or account. (Qur’ān, 3:37)

Through Sufi sources, the concept riḍā is contentment in God and with God, and therefore contentment with one’s destiny as willed by God. Acceptance is a knowledge of self and God, of God in oneself and the self in God, a door to His Mercy through the recognition of the transcendence of His purposes. 

In suffering, in danger, in the bitterness of misunderstanding and offense, He is always near. But we need to know how to recognise His presence and to accept His ways.
"Not My Will but Yours" (Bible, Luke 22:42) 

May Lord grant us faith; may He come to the help of our weakness; and may He enable us to believe and to pray in every anxiety, in the painful nights of doubt and in the long days of suffering, by trustfully abandoning ourselves to Him, in keeping with the Islamic epistemological coda "and God knows best", wa Allāhu aʿlam.