What is God's wisdom in some of His servants not marrying, and what is your advice for strengthening the heart in the face of this destiny?

Marriage is a provision, like all provisions. A servant hastens to receive his provision due to his ignorance of what is beneficial for himself and his ignorance of his Lord's wisdom and gentleness. He may not realize the difference between what he was withheld from and what was stored for him. The servant must be certain that Allah is wise in His actions and commands, and that He does nothing except for a reason, and not all wisdom can be fully comprehended by human minds. A servant may perceive some decree as evil, yet within it lies extraordinary wisdom. Ibn Uthaymeen said: "The divine decree, which is Allah's action, contains no evil; for Allah does nothing except for a reason, even if it appears evil to people."