No — keep it!
(J.R. Miller, "Intimate Letters on Personal Problems" 1914)
In 2 Corinthians 12:7-10, Paul tells of a wonderful experience which he had. He had some great suffering which he called "a thorn in the flesh." He does not say what it was — but evidently it was some physical pain, some think epilepsy, some think a trouble with the eyes, some think a nervous affliction. No matter what it was — it was very painful and seemed to interfere with the apostle's usefulness.
Three times, therefore, he besought the Lord that this thorn in the flesh might be taken away. But the answer was, "No — keep it! My grace is sufficient for you — for My strength is made perfect in weakness." Then Paul learned this wonderful secret — that the physical suffering which was so hard to bear — if accepted by him, brought him a corresponding measure of the strength of Christ!
As you read on, you find the apostle saying that he now rejoiced in his infirmity, because the power of Christ thus rested upon him. That is, the suffering, as keen and as terrible as it was — brought Christ nearer to him, brought more of Christ's strength into his life, and thus fitted him for larger spiritual usefulness!
You can apply this to yourself. You have asked God to remove your thorn in the flesh — and He has not done it. But let me assure you that the words which the Lord spoke to Paul — He speaks to you also. His grace is sufficient for you. His strength is made perfect in your weakness. That is, you will get more of Christ's help in your life, because of the suffering which you are enduring, than if the suffering were to be taken away — you then receiving less of Christ's help, because needing less.