Think about it:
Life is made up of a series of tasks and the success of your day is very much dependent on the success or failure of those tasks. Making your bed is just one task, however, it is a start because if you can take the first step of the day, then the next one gets easier and before you know it you have completed a series of successful tasks.
Making your bed gives you direction for the day; it sets the pace. Once your bed has been made, there is little no more willy nilly-ing around, you have to get on with it. By getting up and getting on with it we might just change the world; one task at a time.
And if your day did not turn out the way you planned? Well, at least you have a nicely made bed to come home to!