Because life goes ahead and your mind is past-oriented, mind and life never meet. Mind goes backwards, lives backwards. Mind is a rear-view mirror. Use it when the occasion arises. Yes, the rear-view mirror in the car has some important function to fulfill. But if you become obsessed with the rear-view mirror, and you only look into the rear-view mirror and drive the car looking always into the rear-view mirror, then there is going to be danger. Then there are going to be accidents and accidents and nothing else.