Shortened for 'progress mess', the mess you make before progressing. For example during DIY, you make mess before the progress is seen

Adj. Something that is expected to have a long lifespan by virtue of having existed for a long time, based on the lindy effect, named for the New York restaurant Lindy's, coined by Albert Goldman and popularized by Nassim Taleb.

when instead of making progress you make a bigger mess than when you started and wish you had just let things be.