Every time I give critique on another's work, or my own, I always want to make sure that the story is "realistic." And whenever I mention that, I always get the, "OMGZZZZ, it's a fantasy novel!" But I think we all need to take a step back, and realize what "realism" in novels actually is: PLAUSIBILITY!
What's plausible in one magical world, might not be plausible in another. Maybe your world is a full-blown fantasy with high mages (I dunno what the terms are), or maybe it's very light on magic, more akin to spells. Either way, when people mention realism, it means realism WITHIN THE CONTEXT OF THAT UNIVERSE.
If you're writing a story in 2019 America with no magic or anything, you can't use coincidences as plot magic to make your character survive. If he's put in a situation where he'd realistically die, like being stabbed in the carotid, he should die. On the other hand, if your world is a magical one where your spell makes you immune from, say, being stabbed, your character should live, as that's within the confines of realism for that world.
tl;dr Keep your fucking discipline. Have a clear set of rules for your universe, and don't stray from them. Plot coincidences ruin stories, and plausible characters making realistic decisions will lead to a better novel.
Source: reddit post