Staying because you’ve already spent years on it is how you spend more years on it. Past effort isn’t a contract.

Time already spent is gone whatever you decide next, which means it cannot tell you anything about the future. Your mind refuses to accept that, so it keeps counting invested years as a reason to invest more, and the argument gets louder the longer you stay. That is a trap closing, not evidence of a good choice.

Ask whether you would start this today, knowing what you now know, with nothing already sunk into it. If the answer is no, the years behind you do not change that. Leaving early costs less than leaving late.