Roller Coaster
When you're on a roller coaster, it's really hard to think about anything else. In retrospect, we say these experiences were fun. In isolation, however, the individual moments that make up the whole wouldn't likely be called pleasurable.
Maybe part of the thrill is being thrust into the present moment, forced to replace any other anxiety or paranoia with the one you're immediately presented with. Maybe we're willing to give up moments of pleasure for extended periods of altered states of mind.