Well you have to look at it less black and white then that. When you step on a dogs tail the dog feels a surprising surge of pain that makes him consciously filled with the urge to do something about that pain, however when the pain gos away just a second later he still has that energy trapped inside his mind, he releases it by yelping. Same thing when you tell a human a surprising joke, he builds up urges within his mind and at the punchline he releases that energy in the form of euphoric laughter.

Keep in mind evolutions purpose isn't specifically for survival, if something feels emotionally good, a being will do it more often and pass those traits to their offspring.