Militaries often encourage this habit, perhaps to give a sense of order to your life and keep things looking uniform?
A majority of people don't make their beds, and seem to get along fine in the world, so it may not really be "necessary" for improving a person's life.
However for the minority that do make their beds, apparently there is also a correlation with a majority of them reporting they consider themselves happy, while a majority of those who don't make their beds admit to being unhappy (via Psychology Today article, referenced in a Mercury News article).
Some people think that making your bed in the morning helps to mentally prepare people for the day, that it's a habit that sets off a chain reaction of other good habits for the day; and it's also just nice to come back to a made bed to sleep in at night.
Could such a little thing have a big positive impact on your life?
Do you like to make your bed, or what do you think of the topic?
