When we're in the here and now, it's much easier to cope with emotions and see them as just that: emotions.  If we get caught up obsessing over the future or past, emotions and situations can take on new (and untrue) meanings as they become attached to stories.  For example, imagine you're turned down for a job.  Naturally you're disappointed.  If you're not present with that emotion and experience it in the moment the mind delves back into your past for all the other times you've felt that way.  Now you feel like a failure and start to carry a feeling of unworthiness into every other interview.  When we stay present, we're empowered to start fresh every moment and we can see every situation with perspective.