It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "He is not a believer of complete faith who does not regard affliction as a blessing and ease as an affliction." The Companions said: "O Messenger of Allah! How is that?" He (peace and blessings be upon him) said: "Because affliction is followed only by ease, and likewise ease is followed only by affliction. And he is not a believer of complete faith who is not in grief (in every state) other than prayer." The Companions said: "And why, O Messenger of Allah?" He (peace and blessings be upon him) said: "Because the one praying is conversing intimately with his Lord, and when he is not in prayer, he is only conversing with a human being."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10903