The following is unedited rambling, I am not responsible for it .
Life is an approximation.
Everything that we do is based on our estimates and assumptions of how long things will take and how much stuff we will need to do it. Then you have a rough idea of how far you are from the shower, and then you have an idea of how much time you plan to spend within that shower waking yourself up. You even have a general idea of how much food you will have to eat to keep yourself from being hungry in a given day. Of course, you have no idea exactly, how much food that is, and you probably don't know exactly how many seconds you spend in the shower. But you know that it doesn't matter, because your life is an approximation, and close enough is good enough for you.