There's a lot of evidence that focusing on gratitude has positive effect on one's well being. And gratitude is important because it's part of reflection, an central ingredient in living life more deliberately. But part of happiness is living consciously, experiencing life deliberately with depth and enjoyment. In this case, savoring is our goal — moving slowly, noticing, and appreciating. One thing that helps is talking to yourself —you can do this silently!— describing to yourself all the positive things going on. So when you're on a walk, instead of being lost in thought, try saying things like "Wow! What a beautiful day! Those flowers are beautiful! That sun feels wonderful." It's even better to do this kind of talk when you're with others. There are so many problems these days that we can fall into the habit of complaining about everything. Sooner or later, this gets old.
So, for increased happiness and health, learn to "savor" your life.