Once you understand introversion and extroversion as preferences for certain levels of stimulation, you can begin consciously trying to situate yourself in environments favorable to your own personality--neither over-stimulating nor understimulating, neither boring nor anxiety-making. You can optimize your life in terms of what personality psychologists call "optimal levels of arousal" and what I call "sweet spots," and by doing so feel more energetic and alive than before.
Your sweet spot is the place where you're optimally stimulated. You probably seek it out already without being aware that you're doing so. Imagine that you're lying contentedly in a hammock reading a great novel. This is a sweet spot. But after half an hour you realize that you've read the same sentence five times; now you're understimulated. So you call a friend and go out for brunch--in other words, you ratchet up your stimulation level--and as you laugh and gossip over blueberry pancakes, you're back, thank goodness, inside your sweet spot. But this agreeable state lasts only until your friend--an extrovert who needs much more stimulation than you do--persuades you to accompany her to a block party, where you're now confronted by loud music and a sea of strangers.
Your friend's neighbors seem affable enough, but you feel pressured to make small talk above the din of music. Now--bang, just like that--you've fallen out of your sweet spot, except this time you're overstimulated. And you'll probably feel that way until you pair off with someone on the periphery of the party for an in-depth conversation, or bow out altogether and return to your novel.
Imagine how much better you'll be at this sweet-spot game once you're aware of playing it. You can set up your work, your hobbies, and your social life so that you spend as much time inside your sweet spot as possible."