Leave every job with at least one person who’d hire you again.

Work is a much smaller world than it looks, and people who worked with you once get asked about you later, usually without your knowledge. One person who would have you back is worth more than a tidy reference letter, because it is a real opinion formed over months. The final fortnight of a job tends to decide it, which is precisely when most people stop trying. Endings get remembered.

However you feel about the place, finish properly: hand over cleanly, train your replacement, thank whoever taught you something. It costs very little and you will want it in three years.