I think it means so much more than deciding not to go out one night, being a martyr for a cause, or throwing yourself into new pursuits.
I think it means making a promise to yourself (an hour of yoga in the morning, twenty pushups a day no matter what, a mini-vacation once every three months for the rest of your life, volunteering on Saturdays…) and keeping it.
The last part is the hardest, but we’re the sum of our habits and the promises we keep. The people I respect the most (and consequently, the most successful) are those I see keeping their promises.
The ones they make to themselves.