Rehab Why doe pain get rid of pain?

Ok had rehab yesterday and he put weights on my ankle. That's a unfair thing when your not expecting it. And then he had the audacity to add 2 new exercises. I know I want my knee not to hurt, but my goodness why is pain how you get rid of pain. The weight was probably just a pound. But it felt like a 100 bounds. This surgery is nothing like I the one I had 3 years ago. I am ready tired of this, but God has put me in this position for a reason. I want to do all of this in a way that is pleasing to God. I'm no better than anyone else to have to endure trials, to all my friends out there who needs a little encouragement about there physical pain. My illness doesn't exempt me from SHARING JESUS.. It’s not awesome to live with this. I have learned if I find  the pain is more endurable.
2 Corinthians 12:7-10(NIV)
7 or because of these surpassingly great revelations. Therefore, in order to keep me from becoming conceited, I was given a thorn in my flesh, a messenger of Satan, to torment me. 8 Three times I pleaded with the Lord to take it away from me. 9 But he said to me, “My grace is sufficient for you, for my power is made perfect in weakness.” Therefore I will boast all the more gladly about my weaknesses, so that Christ’s power may rest on me. 10 That is why, for Christ’s sake, I delight in weaknesses, in insults, in hardships, in persecutions, in difficulties. For when I am weak, then I am strong.
2 Corinthians 4:16-18(KJV)

16 For which cause we faint not; but though our outward man perish, yet the inward man is renewed day by day.17 For our light affliction, which is but for a moment, worketh for us a far more exceeding and eternal weight of glory;18 While we look not at the things which are seen, but at the things which are not seen: for the things which are seen are temporal; but the things which are not seen are eternal.

Isaiah 41:10 (KJV)
0 Fear thou not; for I am with thee: be not dismayed; for I am thy God: I will strengthen thee; yea, I will help thee; yea, I will uphold thee with the right hand of my righteousness.