What? That’s limiting…
More seriously, I learned by doing it wrong in my first original story (now deleted). I crammed it with so much backstory/flashback that I confused my readers and myself. On reflection, I realized I basically had multiple stories in one. So, I spun one backstory off as a regular chaptered story (complete), and the other off as an episodic serial (still WIP). And working on a second episodic to explain where the main protagonist’s swimming instructor came from, so yeah, gotta cut backstory off at a point or it’ll explode with plot bunnies and you’ll never get back around to writing the story you intended to write in the first place.