For what glory is it if, when ye be buffeted for your faults, ye shall take it patiently? but if, when ye do well, and suffer for it, ye take it patiently, this is acceptable with God. (I Peter 2:20)

If a man has a friend and he is absolutely certain that his friend loves him, and if that friend does something to cause him suffering and be troublesome to him, he will be convinced that his friend acts out of love and he will never believe that his friend does it to harm him.  How much more ought we to be convinced about God who created us, who drew us out of nothingness to existence and life, and who became a man for our sake and died for us, and who does everything out of love for us? – Abba Dorotheos (+ c. 570)

If you are not willing to repent through freely choosing to suffer, unsought sufferings will providentially be imposed on you. – St. Thalassios (7th c.)

Suffering cleanses the soul infected with the filth of sensual pleasure and detaches it completely from material things by showing it the penalty incurred as a result of its affection for them. This is why God in His justice allows the devil to afflict men with torments. – St. Maximos the Confessor (+ 662)