A person who has mastered the quality of serenity (menuchah) and has true peace of mind, will feel inner peace and intense joy when going through any life-test. He does not even label the situation 'a test.' Rather, he calls it 'living.'
He utilizes all of his strength and power in any difficult situation. His trust in the Almighty is manifest on a practical level, and this is the goal of his life.
Even though the life-test might persist for a long time (or new ones may arise), he still does not perceive the situation as a burden or misfortune. On the contrary, in such situations his spirit of life becomes aroused because he derives pleasure from being able to rise above his instincts. He does not allow himself to be defeated by anger or despair, and there is no greater pleasure in life than this.
(see Rabbi Yosef Hurwitz of Nevardok - Madraigos Haadam; Rabbi Pliskin's "Consulting the Wise")