And if that shift is a bit unbalanced toward living and experiencing stimulating or pleasurable things in the present... to the point that consequences aren't always taken into account (or risk assesments aren't made), a person can very well be happily chasing things that make them happy at the moment but continually running into unpleasant consequences that make them unhappy, only to redouble efforts to be happy right now
That behavior is what addicts do when they come down - they try to get high again.
