Stick to the program, temper your spending appropriately, and eventually YNAB will see you spending last month's money rather than that which you've just earned.
YNAB's primary mission, as you might expect, is to help you curb overspending and avoid living from paycheck to paycheck. And perhaps you have more money than you thought? Because, hey, if you don't want to spend every single penny you have and more, you absolutely do need one. Just in case you need to be told explicitly what to do, along comes YNAB - short for You Need A Budget.