Re: a thorn in the flesh--The Bible is clear: a thorn in the flesh is a messenger from Satan. And God's grace is always sufficient!
God's most powerful word to me is this, "Trust Me." I think that is why, in my life, anxiety has always been a "thorn in the flesh." As I've grown in my walk, I see it as a catalyst to pray more and to trust God more. I believe what Jesus said about worry--that I have no power--NONE--over anything, or anyone, or any situation. When the messenger of Satan drives me to worry, I drop to my knees. Anxiety not handed over to the Lord is a faith issue--and God gives me His sufficient grace to resist its power. His grace is always there for me, and it is sin on my part if I do not avail myself of His grace.
I posted the scripture passage below on the thread "God controls Satan," because it is such a good example of just that. Or you could also say, "God allows Satan" or, "God gives Satan permission," because He does. In Paul's case, it was given to keep him from exalting himself. As much as God had revealed to Paul...none of us can fathom the revelations!...God sent the "messenger" from Satan to buffet Paul, to keep him from the sin of pride--particularly, of exalting himself. So how do we identify such "thorns"? I would say that they are temptations, or trials, or situations, or calamities that seem to have no end--these can take many forms--and we want them to go away. And though we often pray that God will "take it away," we know that when He doesn't, it is for our good and His glory. That is the essence of proving our trust.
A thorn in the flesh is an affliction. When Paul speaks of "buffeting," I think of it as invading, or intruding, or persisting; this repeated act of assault requires resistance, which in turn builds strength and endurance. The good news is, that no matter how difficult the challenge, we have victory in all things when we trust Christ. "I can do all things through Him who strengthens me." Philip4:13
2Cor12:7-10 "And because of the surpassing greatness of the revelations, for this reason, to keep me from exalting myself, there was given me a thorn in the flesh, a messenger of Satan to buffet me--to keep me from exalting myself! Concerning this I entreated the Lord three times that it might depart from me. And He has said to me, 'My grace is sufficient for you, for power is perfected in weakness.' Most gladly, therefore, I will rather boast about my weaknesses, that the power of Christ may dwell in me. Therefore I am well content with weaknesses, with insults, with distresses, with persecutions, with difficulties, for Christ's sake; for when I am weak, then I am strong."
Consider Peter when Jesus said, "Simon, Simon, behold, Satan has demanded permission to sift you like wheat; but I have prayed for you, that your faith may not fail; and you, when once you have turned again, strengthen your brothers." Luke 22:31-32 It encourages me that Christ is praying for us when we encounter our "thorns." Jesus is praying for us!! His desire is that we have victory, though when we fail, we can turn again and strengthen others.
And let's not forget Job...
Now this quote from G. Campbell Morgan (found in the SI Text Sermons) and I'm through:
GOD'S SUFFICIENT GRACE
My grace is sufficient for thee. Upon that great word many a weary head has rested; many wounded hearts have been healed by it; discouraged souls have heard its infinite music and have set their lives to new endeavor until they have become victorious. That stake in the flesh, that messenger of Satan, is in My grace. It is part of My method. The stake in the flesh is sent. The messenger of Satan is My messenger. That is not something that is against you, but for you. This hard and difficult and trying circumstance is not something outside My providence, My economy, which you must overcome with My help: it is of My purpose, it is My plan. I am high enthroned above all the powers of darkness, and to the trusting soul Satan himself is compelled to be a means of My grace. All your suffering is in My economy. I have poised in My own hand the weight of your burden and know it. Everything that is imposed upon you is under My control. My grace is sufficient for thee. It is enough for you to know that what you are suffering is part of my discipline, evidence of My love.