Bed levelling is the chore that never ends, and for years I treated it as a ritual: the folded sheet of paper, the four corners, the slight drag, the nudge, round and round until I lost patience and called it good enough. Then the first layer would be perfect on the left and squashed on the right, and I'd do it all again next week.
The thing I was refusing to accept is that "level" was never the real goal, and the bed isn't flat anyway. A glass or steel sheet over a heated plate has a gentle warp to it, and no amount of corner-twiddling fixes a dip in the middle. You can get all four corners spot on and still have the centre sitting a tenth of a millimetre too high or too low, which is exactly enough to ruin a first layer.
What actually fixed it was a probe and a mesh. Let the machine touch down on a grid of points, build a height map of the bed including its warp, and compensate in software as it prints the first layer. Suddenly the corners and the middle were all the same. The paper went back in the drawer. I still wipe the bed and check the probe is clean, because a smear of grease throws the readings off, but the war is basically over. I just had to stop pretending the bed was a flat plane and let the firmware deal with the truth.