Most people have heard of the Eastern teaching that it is important to exist in the moment. It can be hard to train yourself to observe what is right now (and not to bog down in thoughts of what was and what will be), but the philosophical teaching that underlies that idea--the reason that staying in the moment is so vital--is equally important: Everything is changing. All the time. And you can't stop it. And your attempts to stop it actually put you in a bad place.