Alas, today is not a Monday holiday for me. But why are Monday holidays better?
Friday holidays are too easy to waste and they don't help much. When a Friday is off, it makes the previous week shorter. Well that's nice, but when I start a week I am prepared to end it in five days, so the Friday just ends it early. This can be disorienting: "Why am I not at work?" Fridays, being at the start, make it easy to think "well I have two more days, I'm in no rush to do anything" and next thing it's time to sleep and you've done nothing.
Come Saturday and the Friday had no lasting impact.
Mondays are much better for holidays. They extend the weekend unexpectedly. When it is Sunday night and you are dreading the coming day, thinking of all you couldn't do yet, there's your extra day. The new week is shorter and you start it more refreshed. Even better, when it is Tuesday, you can know that without that holiday it would still be Monday. This is obvious by principle of time moving faster when not miserable, so we can clearly see that with a Monday holiday the day effectively vanishes, literally removing one day from the week and acting as a type of time travel.