[The young writer] must train himself in ruthless intolerance. That is, to throw away anything that is false no matter how much he might love that page or that paragraph.
– William Faulkner
others have said it, to "kill your darlings," which is also similar to sunk cost bias in business. i believe it applies much more generally, as well.
how hard is this for you? have you trained yourself to be a cold, hard killer?