How? That's a question to all you Sunday-First users, I don't really get the problem.
Starting on Monday means that you have five work-days combined. Then two free days combined. There are several good things about this:
1. It implicitly teaches that one first has to do the work before one can have a time of to enjoy the fruits of one's labour. Monday-First teaches good work morals.
2. If you go away during the weekend, you can see the entire trip in one bloc on your calendar, instead of seeing you leaving on Friday or Saturday, then having to write something again on the Sunday that is all the way on the left side - and even one row down! - to show that you're coming back. Monday-First makes your calendar neater and easier to read.
3. If you're Christian, then you get Sunday - the holy, seventh day - when God rested, as the correctly seventh day of the week. Clearly Monday-First is more in line with God's will.
4. In the interest of being encompassing for all the Abrahamic religions, Monday-First concentrates all the spiritually most important days - Friday for Muslims, Saturday for Jews and Sunday for Christians - in one easy to comprehend bloc. Much better than having them split on two sides of the calendar.
5. Monday-First is the internationally agreed upon standard. Standards are good. Therefore, Monday-First is good.