So, "I woke up one night in a cold sweat, with a mysterious rune nearby and now I can use magic" is totally fine. Perfectly explained. It has a full narrative weight.
"I woke up one morning in a cold sweat, and the world seemed clearer and now I can cut the wind" is utter bollocks. Nothing is explained and it is completely without reason, and therefore it cannot be done.
And yet... I did basically the exact same thing. You just feel like you know the story of the mysterious rune, but since you aren't familiar with the correct literature, the world seeming to be more clear doesn't mean anything to you.