A: What’s wrong with John? He keeps missing the deadlines for his assignments.

B: We need to give him a heads-up. His behavior will lead him down a slippery slope to ruin.

Note: This idiom, borrowing the image of a person falling all the way down a slippery slope, refers to “a course of action that seems to lead inevitably from one result to another with unintended consequences.” That is, things go from bad to worse if you let them be.