Many of us like to think that we're these rational economic actors. The power of logic courses through our brains.
But nearly all of us fall for the "sunk cost fallacy". We've invested a lot of time, money, effort, whatever into X. And because we've invested so heavily, we have to continue with X.
But that investment is gone. You won't get it back. It's yesterday's cost.
So it shouldn't figure in today's decision.
Take action: What decision are you shying away from because of your previous investment?