"And we know that all things work together for good to them that love God, to them who are the called according to his purpose." (Rom 8: 28)
A certain woman had two teachers: one who served his students and another whose students served him.
The first loved to listen, loved to give advice that helped others do work they could find joy in. He gave strong reproofs to students he knew well and who trusted him, reproofs grounded in his understanding of their goals and weaknesses.
When their time together drew to an end, she went to him, tried to express the debt she felt she owed him, to explain how grateful she'd been to count herself as his pupil.
But he said, "Don't thank me; thank the God who allowed us to cross paths."
The second teacher loved to be listened to, gave sharp reproofs at a glance without considering their implications, wanted others to do work that pleased him. She struggled under him, asked if there wasn't a better way.
When their time together drew to an end, he called her into his office and told her that he had been good for her--if not through his counsel than through his resistance. Either, after all, would contribute to her growth, and someday she would thank him.
"No" she said. "But I will thank the God who allowed us to cross paths."