One is a result of circumstances. If something bad happens, like you get a flat tire, then you're in some negative state of emotion. Most people are ruled by this, and since most circumstances are out of our control, we spend a large portion of our time in some state of unhappiness or frustration.
The other is trying to be at peace. If you're basically at peace then the flat tire doesn't ruin your day. It's just something to deal with. Things happen, you deal with them, life goes on, and you're mostly thankful for what you have.
The author's 20 minute comment, I suspect, is that he practices mindfulness meditation, and is therefore never longer than 20 minutes away from resetting his mind to a more balanced state.
Plus there is nothing new here. This is the ancient philosophy of stoicism. See "A Guide To The Good Life: The Ancient Art of Stoic Joy"
What seems natural for most of us, though, is to become desensitized to what's good and feel only about the surprises, which eventually end up negative (mean-reversion and things over-enthusiastically taken for granted - I'll always win, they'll always love me, etc.)
I think knowing that helps a little. Just like it helps knowing that your blue mood when you're sick will pass on its own as you recover.
Some people are naturally more or less happy, I'm sure, in their baseline no-surprise state. I wouldn't worry about it until someone figures out how to change it. As long as you have energy to want+do things, you're ok.