In my experience finishing is easier than quitting:
- when the thing you’re currently doing is not something that you’ve consciously chosen for yourself but that you’ve ended up doing because everyone else in your social circle / tribe was also doing it (like applying for college, getting a real job, locking yourself up in a certain lifestyle, marrying, or even following a certain religion) — the need for consistency and approval of others will be enough of an obstacle to prevent you from even pondering other options, let alone quitting
- when the investment that you’ve made so far seems too big to quit. Often people don’t even think about switching careers because they’ve spent all those years getting to where they are now. The investment bias is against them. This bias tells you not to quit even if quitting would be objectively a good thing to do. It’s a common thing in court cases (you’ve spent so much time, energy and dollars fighting this bastard that if you quit now you you’ll lose this investment). They often think that the only way they can get part of this investment back is to persist and hope that the opponent will lose and pay for your expenses.