Let us not get confused here. By letting go, I don’t mean surrendering or giving up, but rather letting go of the stories we tell ourselves that we can’t do something, the expectations and judgments we experience as we move through our practice, and our egos that push us too hard. So often these judgments and harsh criticisms hold us back, keeping us from our true potential, hiding us from the brilliance within. - See more at: http://yoganonymous.com/capricious-yogi-rachel-wallmuller-yo...

In the November 2009 issue of Yoga Journal, the article “great escapes” describes four types of yoga retreats: home, do-it-yourself (with friends), urban, and luxury. I was relieved that they covered a variety of retreats, which mean wildly different things to different people.

The word “retreat” literally means to withdraw, and I subscribe to that definition. My ideal yoga retreat would be inwardly focused, a major departure from my normal life. By “departure,” I don’t necessarily mean leaving home. The setting can be familiar or foreign (although novelty does make an impression). Rather, this departure must be mental: a separation from my everyday idea of myself.

in or on, or relating to, the inside or inner part;
internally.
privately;
secretly:
Inwardly, he disliked his guest.
within the self; mentally or spiritually:
He promised to stay inwardly calm.

So much of what is written about Yogi Bhajan's sayings or teachings in respect of happines is about surrending oneself to the Infinite, to God's grace, et. or forgetting oneself. I can't find an exact translation, but I would personally go with 'surrender' in your context.

http://www.3ho.org/3ho-lifestyle/aquarian-age/power-surrende...

http://www.spiritvoyage.com/40GS_releaseFear/day23.html

When I met Yogi Bhajan, he told me, "If you want to be happy, forget about yourself—and serve others." And he gave me an avenue for service; he gave me the privilege of teaching Kundalini Yoga. Teaching has been one of my greatest joys. As many of you know, the oath of a Kundalini Yoga Teacher is, "I'm not a woman, I'm not a man, I'm not a person, I'm not myself, I'm a Teacher." And this affirmation of "forgetting about oneself" works the magic of allowing you to be an instrument to bring hope and inspiration to others, as well as to share a life-transforming technology. And, of course, this makes you feel wonderful.
http://www.3ho.org/3ho-lifestyle/prosperity/attitude-gratitu...

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Note added at 11 hrs (2014-09-23 18:25:57 GMT)
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Goodness me, the above should read "happiness is about surrendering oneself". I must be tired (I am tired).