From Meditations 5.20, translated by Gregory Hays:
The mind adapts and converts to its own purposes the obstacle to our acting.
The impediment to action advances action.
What stands in the way becomes the way.
How very close this is to that trite old stumbling-block-to-stepping-stone bromide — and, having been just a little bit more clearly thought out and more ably expressed, how much deeper! Some schlock is wisdom sung off-key.