It works like this:

Mondays you only give 50%. It’s monday, after all.
Tuesday you give around 85%. You don’t have Monday as an excuse anymore. Tuesday is right there in the meat of the week.
Wednesdays you can pull it back a bit. People are using the word “hump” in a professional setting, so you can’t be expected to do too much.
Thursdays you start winding down. You’ve crested the hill and now momentum is carrying you towards your weekend plans.
Friday you don’t even go in. You’re still drunk from Thursday.