Well there are a couple of possibilities. The first, one can translate it just as you asked: fortitudo e dolore venit "strength comes from/out of pain" But if you want to simplify it, one can just use: fortitudo per dolorem "Strength through pain"
Previous pinner wrote----Always be thankful for what you already have—which is so very much! “Those who live in thanksgiving daily. are among the world’s happiest people. The power of gratitude is immense.” –Joseph B.