To increase happiness, do something fun. To increase meaning, do something challenging.
I have been happy plenty of times in my life. I'm not talking about happy as an extended state of mind, but as a burst of unhindered emotion with no guilt or regret. It almost always happens when I play football or when I watch Chelsea win a game. It is essential. But experiencing it too often will make it boring. The law of diminishing marginal utility sets in and progressively drives away the happy feeling.
If at that point, I decide to take up a challenging activity like writing a blog post or preparing for a customer pitch or going for a long run, I rarely have the motivation to do justice to the task at hand. I end up doing just about enough to tick off a checklist as opposed to really take the challenge (that the task is) head on and come out successful and be able to reflect back upon a job well done.
While I agree with what Chris says, the context in which we do something fun or something challenging makes a good deal of difference in increasing happiness or meaning.
When I plan my week, I intersperse things that are challenging and fun in an attempt to increase both. When most of the items on my plan fall into neither category, I know I'm in trouble and need an overhaul in what I'm doing.
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