When [Eleazar] was about to die under the blows, he groaned and said: “The Lord in his holy knowledge knows full well that, although I could have escaped death, I am not only enduring terrible pain in my body from this scourging, but also suffering it with joy in my soul because of my devotion to him.”Suffering terrible pain with joy in our souls--this seems to be almost impossible. And yet, slowly, over many years, if you can learn to accept suffering as God's will for you that day, it begins to happen. It's very strange because the suffering is no less suffering, in fact it might be even harder than before, and yet, that joy begins to grown and it brings peace with it. Part of that peace, I think, is the realization that this is what you are called to do. It's not your part to fix whatever is causing the suffering, or try to manipulate people into doing something that would make your suffering stop. You just pray and offer it to God and endure--but it's a joyful endurance nonetheless.
I'm not an expert at this by any means, but I do sometimes experience it.