Stay in the moment

Have you heard of "mindfulness"? Chances are you have - it's very much a word-of-the-moment, but do you understand it?  Chances are you don't.  And that's partly because it's one of those concepts that can mean different things at different times to different people.  I have come across it in relation to stress (not me) and my, perhaps simplistic, take is that if you are worried, depressed, stressed or whatever, then it's almost certainly due to something that has happened in the past, or something you anticipate will happen in the future,  So if you can force yourself (or be forced) to concentrate all your energies on this instant - the here and now - you can block out the past and future and in time get a different, more dispassionate perspective on your problem - whatever it is.  Taking this to the extreme, there is a philosophical school of thought called "presentism" which holds that only the present is real - neither the past nor future exist.  And my head is beginning to hurt!