By the practice of gratitude I mean a lot more than observing all rules of etiquette about when and how to express gratitude to another person. Or even cultivating sincerity in one's observance of these rules of etiquette. Don't get me wrong; these are important! But the practice of gratitude I have in mind involves learning how to be grateful for your life as a whole, to dwell in that gratitude deliberately, and out of the strength gained in that dwelling to live out the sort of life you know you're supposed to live: a life joyful and bringing joy to others.
Here are some things I am learning about how to get better at practicing gratitude.
The practice of gratitude involves reflecting on all the good things about your life, in absolute rather than relative terms. Suppose you have an injury or illness which causes you pain and keeps you from doing all the things you'd do were your body as healthy as it could be. Well, then, relatively speaking, you might judge yourself to be in poor health, and have a sense of disappointment about this. But if instead you think of the fact that you are alive, that you can breathe and eat and digest your food, hear music and see trees and birds, communicate with friends and family and love and be loved by them, well, then absolutely speaking, you can recognize the great goodness of your life. This doesn't mean you forget about your illness or injury. But what this change of focus does is enable you to see your life as healthy in spite of your illness, rather than unhealthy because of it. We can do this in other spheres of our lives as well: possessions, finances, relationships, social status, and so on.
Practicing gratitude also involves recognizing that you are not really entitled to much of anything. The universe owes you nothing; God owes you nothing. Maybe you think God owes you something given that you exist; but consider that God never owed it to you to cause your existence in the first place. Other people owe you a bit, but just a bit: when you were young your parents owed you life's basics; they didn't owe you nice things and they didn't owe you whatever it took to make you happy. Strangers are free to ignore you, except perhaps in some extreme circumstances in which they ought to provide some help--for example if a stranger is witnessing someone assaulting you that stranger owes it to you to do something or other to help you. The government cannot treat you unjustly and while there's lots of disagreement about what a government owes its people I think we can agree that you are not owed a government in the first place, good or bad, minimal or maximal. Your friends owe you things insofar as they're your friends, but this is complicated by the fact that the friendship itself which creates these demands is not itself owed.
Thus, all in all, there's very little you deserve. And this means that most of us are not owed whatever we do not have but want, and were not owed what we do we have but take for granted. Recognizing we're not owed what we lack takes some of the sting out of not having it; and recognizing we weren't owed what we have helps cultivate a sense of delight, even surprise, that we have what we have.