Improving decision quality is about increasing our chances of good outcomes, not guaranteeing them. - Annie Duke

When you overfit decision quality to outcome quality, you risk repeating decision errors that, thanks to luck, preceded a good outcome. You may also avoid repeating good decisions that, because of luck, didn't work out.

As you already know, grit is good for getting you to stick to hard things that are worthwhile, but grit also gets you to stick to hard things that are no longer worthwhile.

Chess contains no hidden information and very little luck. The pieces are all there for both players to see. Pieces can't randomly appear or disappear from the board or get moved from one position to another by chance. No one rolls dice after which, if the roll goes against you, your bishop is taken off the board. If you lose at a game of chess, it must be because there were better moves that you didn't make or didn't see. You can theoretically go back and figure out exactly where you made mistakes. If one chess player is more than just a bit better than another, it is nearly inevitable the better player will win (if they are white) or, at least, draw (if they are black). On the rare occasions when a lower-ranked grand master beats a Garry Kasparov, Bobby Fischer, or Magnus Carlsen, it is because the higher-ranked player made identifiable, objective mistakes, allowing the other player to capitalize.