how do you write a character who is lying to the reader without it feeling like a cheap trick when it's revealed

first person narrator. she's an unreliable one, by design. she's been shading the truth the whole book, leaving things out, telling herself a version of events that isn't quite what happened.

the reveal lands around 80%. and my worry is that it'll feel like a gotcha. like I tricked the reader rather than letting them feel the truth was there underneath the whole time.

I've read books that do this well, where on a reread you can see all the cracks she was papering over, and it feels earned and devastating. and I've read books where it feels like the author just withheld information to spring a surprise, and you feel cheated rather than moved.

what's the actual difference between those two? is it about fairness, like planting enough that an attentive reader could have seen it? is it about the lie being emotionally motivated rather than plot-convenient? I can feel the difference as a reader but I can't articulate the rule, and I need the rule to make sure I'm on the right side of it