>it's just hard to throw away something I've invested so much time and effort into

It’s called sunk cost fallacy.

“Individuals commit the sunk cost fallacy when they continue a behavior or endeavor as a result of previously invested resources”

That is, you only continue because you don’t want to loose your time and effort without anything in return. WITHOUT taking into account weather the venture has failed already. Your investment makes no difference to the outcome of this relationship and the best thing is to cut your losses before you sink any more of your time that you can’t get back into a failed project.