when do you quit for something different

If you want a significant change in your results, then you probably need a significant change to your strategy.
Working harder on your current strategy is unlikely to move the needle.
Before you work harder, work on the right thing.
Play better games. Win better prizes.
— James Clear

When is it time to quit and search for something different? You may be very close to making it all worth it, but what if it's just the sunk cost talking and that moment is never to be seen?