Non-gainful gain?

The past couple of morning zazen sittings were outstanding. A couple of weeks ago, I had an electronic conversation with one of my gentle readers about the apparent tension between the Zen concept of no-gain and the feeling that we get gain because sometimes things are just better somehow after sitting. We must get some kind of gain out of what we do, as we keep going back for more, and Zen isn't the type of spiritual practice Americans would do out of tradition or social obligation. Moreover, I did not get into Zen practice as part of a search for any enlightenment or ultimate revelation (for now, I'm content with the transient, impermanent human truth works for me at the moment). Rather, I was simply trying out something that seemed like it might create a space of tranquility in a chaotic mind. At the time, tranquility was a major gain. Of course, with Buddhism being a non-dualistic philosophy, it could be that gain and no-gain aren't in any tension at all, but are somehow one and the same and can be held in a perfect balance.