“There are two different kinds of activities we enjoy: pleasures and engagements.
Pleasures are activities that have clear, enjoyable bodily sensations ― pleasant raw feelings.
Engagements, on the other hand, are activities we very much like doing, but they’re not necessarily accompanied by any pleasant sensations at all. Rather, we lose ourself in the activity and enter a state of total immersion.”i
“Pleasures are activities that revolve around pleasant bodily sensations. They involve little or no thinking. Touching, tasting, smelling, seeing, hearing, and moving all can directly evoke pleasure.
Basically, the sensations themselves are the good part.
A hot shower when you’re covered with muck, a cool breeze on a spring day, and sitting down in front of a fire on a snowy evening are all examples of pleasures.” 
more examples of pleasures:
• eating your favorite dessert
• smelling your favorite scent
• listening to a new, catchy song
• looking at a beautiful combination of colors
• getting a massage
• scratching an itch
• drinking water when you’re really thirsty
• finally using the bathroom
• ingesting nicotine, alcohol, heroin, etc.
• sex (which can also be an engagement)
“Despite the results pleasures reliably bring, rapidly repeated indulgence in the same pleasure doesn’t work. Though the first taste of French vanilla ice cream is truly satisfying, the pleasure of the second taste is significantly less than that of the first, and by the tenth taste, it’s largely just calories. This process is called habituation. Our brains are wired to notice events that are novel and disregard those that aren’t.” 
“Unfortunately, we become accustomed to pleasures very readily (habituation), often requiring larger doses to deliver the same degree of enjoyment as originally (tolerance), and many pleasures even have negative aftermath (addiction).” 
“Sadly, you can’t enjoy a pleasure all day long. By their very nature, pleasures satiate. Eating an entire cake in an afternoon or listening to a new song twenty times in a row are ways of deadening yourself to a source of pleasure. Pleasures must be spaced out sparingly to maintain their potency.
Similarly, it’s best for pleasures to be varied. The French do this at meals by serving many small courses instead of one large one. Variety is the spice of life, because it’s the natural enemy of habituation.” 
“There’s a state that many people value even more than pleasure ― the state of total immersion in an activity. Psychologist Mihály Csíkszentmihályi called this flow, because it often feels like effortless movement. It’s the experience of being completely absorbed in the doing of something. There’s a feeling of energized focus and enjoyment. Every action and thought follows from the previous one, like playing jazz. Your whole being is involved, and you’re using your skills to the utmost.” 
“Engagements are activities that lead to a state of flow, or at least have the potential to do so. With engagements, it’s the total absorption that we like, rather than the presence of pleasure. And unlike pleasures, engagements involve quite a lot of thinking, though much of it isn’t conscious.
examples of engagements:
• playing chess
• watching a movie
• driving fast on curvy roads
• playing the piano
• rock climbing
• playing video games
• solving crossword puzzles
• listening sympathetically to another person’s troubles
Playing a close game of tennis that stretches one’s ability is enjoyable, as is reading a book that reveals things in a new light. And any piece of work well done is enjoyable. None of these experiences may be particularly pleasurable at the time, but afterward we think back on them and think, ‘That was fun,’ and wish they’d happen again.
components of an engagement:
• there’s a challenging task that requires skill
• we possess the skill necessary to meet the challenge
• we concentrate, our attention is fully engaged
• there’s a sense of control
• there are clear goals
• we get immediate feedback at each step
• there’s a deep feeling of immersion, absorption, involvement
• our sense of self vanishes
• we lose track of time, time flies by” 
I can think of one particularly memorable example of ‘our sense of self vanishing’. In college, after finishing a long, difficult exam, one girl said to another, “I forgot I existed.”
[Pannenkoek] “There’s a sweetspot that leads to flow. If the activity is too easy, you become bored. And if it’s too hard, you just feel frustrated or overwhelmed.”
“Engagements generally don’t habituate as easily as pleasures do.”  In fact, there’s a sense in which engagements can reverse-habituate ― the more time you put into them, the more enjoyable they can become.
“People rarely succeed unless they’re having fun in what they’re doing.” 
“That’s the way you learn the most ― when you’re doing something with such enjoyment that you don’t notice the time passing.” 
“When we partake in pleasures, perhaps we’re just consuming. The smell of perfume, the taste of cake, and the feel of a back rub are all high momentary delights, but they don’t build anything for the future. In contrast, when we’re engaged, in a state of flow, perhaps we’re investing ― and absorption, the loss of one’s sense of self, and the feeling of time flying by may be evolution’s way of marking the achievement of psychological growth.” 
“One reason for the widespread wariness of pleasure is that it gives no lasting benefit. Pleasure feels good in the moment but we’re no wiser or stronger afterwards. Engagements are different, though. They challenge us and make us extend ourselves. When we enter a state of flow, hard work becomes effortless.” 
- Martin Seligman
- Jonathan Haidt
- Jonathan Haidt, Martin Seligman, Chris Niebauer, & Wikipedia’s Flow (Psychology) article
- Dale Carnegie
- Albert Einstein