Why do we keep throwing good money after bad?
The more you've already poured in, the harder it is to walk away - even when you should.
The sunk cost fallacy is the tendency to continue an endeavor because of previously invested time, money, or effort - even when stopping would be the rational choice. The money is already gone; only future outcomes should drive the decision.
You sit through a bad two-hour movie "because you paid for the ticket", losing time on top of money.
What you've already spent is gone regardless of what you do next - only future costs and benefits should matter.
Decide from where you stand now, not from what you already lost - the past money is gone either way.
Spent is spent - only the future counts.
Learn the idea and practice English at the same time.