Practice of Gratitude
One of the "open secrets" typically revealed through practice is that gratitude opens for happiness.
This is of course opposite of the conventional view: a limited and specific set of situations leads to happiness and then gratitude. This "open secret" is - as far as I can tell now - that any situation can trigger gratitude, which in turn leads to happiness. Gratitude is the effort which invites in the grace of happiness.
And we can practice this in a similar way as the Tibetan practice of tong len.
First, we find gratitude for everything that it is easy to find gratitude for. Everything that goes well according to our limited human view, anything that alignes with what our human self sees as desireable.
Then, we can expand this to find gratitude for anything and everything that seems neutral, that which we earlier may not have taken time to explore in terms of gratitude.
And finally, we can expand it to find gratitude for that which our human self does not like so much, that which is not aligned with our personal preferences. We can allow this into our experience of gratitude, and also explore how each of these situations are a gift. What can I learn from it? What is the gift in it?
I find that when I do this, it quite literally transforms my life. It goes from being more contracted and sad, to wide open, receptive and - yes - grateful for all there is, as it is. And this also frees energy so I can be more actively engagaged in my life. It gives benefits all around.
Another way to practice this, which I find to be a good complement, is to place my attention at my physical heart area and use "thanks, thanks, thanks..." as a mantra (or something similar).
And as with any practice, after a while it becomes a flow which takes on its own life. Eventually, it just happens on its own, wordlessly, day and night.
It comes from, and leads us into, Big Mind or selflessness (realization of no "I"). And it comes from and leads into Big Heart, heartcenteredness and fullness.