Lives and deaths
How to survive
Surviving is not the objective — searching is. Lives are a budget you spend on search time, and most players spend theirs badly.

Your budget
3 hearts + 1
A last chance follows the third heart. Counting only the hearts will surprise you in both directions.
Cost of a death
Position, not progress
You drop everything where you fell and restart at the entrance. Anyone can pick the keys back up.
Distance is a two-key combination
Crouching does not save you once you have been seen. “the only way we can outrun the killer is if we sprint and slide.” Shift to sprint, Shift and C together to slide. The slide is what carries you around a corner fast enough to break the chase, and it is the part most players never learn.
Hiding beats running
Running preserves a life. Hiding preserves your position, which is the expensive thing. If there is a hidey hole or a clock in the room you are already in, taking it costs you seconds; being chased across the building costs you the whole sweep you had built up.
The Mines is the gentler chapter
If you are burning through lives in the school, the second chapter is genuinely more forgiving — Thomas is audible from much further away and cannot close distance instantly the way the Cat can. The badge rates say fewer people finish it, but that is because fewer people try it, not because it punishes harder in the moment.