Why do you spend a 500k note slower than five 100k notes?
The same money in your pocket spends faster when it is broken into small change.
People are more willing to spend a sum when it is held as several small bills than as one large bill of equal value. A big note feels harder to break, so it quietly acts as a barrier. Small bills feel like loose, spendable change, so they slip away one purchase at a time.
With one 500,000 VND note you hesitate to break it for a snack, but the same 500,000 in 10,000 and 20,000 notes leaks out on iced coffee and parking before lunch.
To slow your spending, hold your cash as large bills; to loosen it, break it into small ones.
If you tend to overspend, withdrawing cash as large notes builds in a speed bump that needs zero extra willpower.
Big note = a wall you do not want to crack. Small change = water through your fingers.
Learn the idea and practice English at the same time.