If you are driving and more concerned about what's behind you than what is in front of you it won't be long before you crash. If in life you are always thinking and focussing on what happened in your past, of what could have happened, or on what you think should have happened, then you shall be missing out on the pleasures that only the present can offer. There is a big difference in watching someone eat a bar of chocolate on a TV ad, from actually eating in yourself. If you do not live in the present , then your life is just a big Tv ad with everything always out of your grasp. You are shown the potential but you can never have it in your hand as you are not in the present to enjoy it. The past and future are just advertisements and you will need to be in the present time to buy and enjoy anything you want.