It's similar to the "count to ten" principle, before yelling at someone.

I'd also assume that it may be that having the weekend could put one in the mindset of relaxation and cause procrastination at the start of what could be an intense process that requires drive (depending on individual's circumstances).

Or maybe it's kinda the opposite where if one were to quit on say a Monday instead, there's a good chance that the work week mindset holds, kicks the individual into being productive (maybe more productive than usual out of necessity), and then that weekend would be very much needed to wind down/refresh and reflect on the progress that was made.

Again, just my assumptions, but seem like likely scenarios that could play out

Edit: spelling