Paul asked three times for the thorn to be taken away. Three times is not a passing request; it is a campaign. And the answer he received was no — but a no with something attached: My grace is sufficient for thee: for my strength is made perfect in weakness.
We tend to want grace to be the thing that removes the problem. Paul discovered it was the thing that made the problem survivable, and then something stranger — the place where God's strength became most visible. The thorn stayed. The grace was enough. Both were true at once.
This is not a recommendation to enjoy suffering, and Paul does not pretend to. He calls it a messenger of Satan to buffet me. He wanted it gone. But he stops interpreting the unanswered prayer as abandonment, and that changes everything about how he carries it.
Most of us have a thorn — a limitation, a temperament, a chronic difficulty, a relationship that will not resolve. The temptation is to treat life as suspended until it is dealt with, as though real usefulness begins after the removal. Paul's conclusion runs the other way: most gladly therefore will I rather glory in my infirmities, that the power of Christ may rest upon me. The weakness became the address where the strength turned up.