I too have studied some Zen but mostly very casually as part of my martial arts training. It was definitely helpful. As I learned to be fully present and live in the now happiness began to come more naturally.

The real “game changer” was when I stumbled across this by Oriah Mountain Dreamer:

And I found that I can do it if I choose to — I can stay awake and let the sorrows of the world tear me apart and then allow the joys to put me back together different from before but whole once again.

Now when I encounter something that causes un-happiness I know that it will pass and the joys will push it away into a distant memory.

I don’t think this alone, without my study of Zen and practicing living in the now, would have had the same level of impact. But because I was already open to the fact that happiness is a choice this really resonated and has become a mantra for me.