It gives me great pains to throw something away that is still useful. This proclivity to hold onto things is constantly on the verge of A&E Hoarder territory that I rationalize away as my inclinations are towards usefulness, not sentimentality. This is willful self deception.
In the printshop, people discard old prints, old paper, and test proofs. I collect these, and layer over them each time I print something else. I print multiple times on a found piece until it's become something new, unrecognizeable to the original artist, and perhaps better, perhaps not. I have a drawer full of these in progress, but here are a few that I deemed "finished." Mediums include lithography, screenprint, monoserigraphy, letterpress, etching, relief, monotype, and hand drawing.