Sunk Cost Fallacy
This is the idea that you’ve already invested x amount of time or money into a project or idea. Therefore no matter whether it makes any other rational sense or not you are still compelled to carry on with the task/idea because otherwise you feel like you have wasted whatever you’ve already invested.
Most people have done this at some point in their lives. Being aware of our failings as humans makes it easier for us to be rational and hopefully stop ourselves from investing too much time and energy in a futile endeavour.