Even letting such a thought cross my mind is enough to drive that special state of mind away. There has to be complete, unthinking, fearlessness and confidence for me to experience it. Tango is such a mind-game, for a whole gamut of reasons, that it's very hard to achieve that state of empty-headed awareness.
Like Light Sleeper, it was almost easier when I was a complete beginner and newly-in-love with tango. Four years on, like in most relationships, things have become more complex! I'm still in love, but notice the quirks and blemishes more - and it's harder to get enthusiastic.
Yes on the first part, Madahlia. Among the characteristics of flow are a loss of self-consciousness and one's sense of time.
Also, experiencing flow less often once one progresses past the beginning stages of learning has been reported by quite a few. I believe this is because another characteristic of flow is the balance of challenge and skills. I think when you are a beginner you have plenty of challenges and many opportunities to rise to these challenges as your skills increase. When you reach an intermediate or advanced level, you may find less challenges depending on your community and many other factors. Your perception and mentality also have a lot to do with it. If you don't think there are any challenges for you, you may become bored. On the other hand, as Madahlia mentioned, if you are overly focused on your shortcomings or on more challenges than you can handle at one time, you may become overwhelmed.
Many people don't relate to the idea of balancing challenges and skills when it comes to flow because they think it is more about connection. And that is fine. But even if your focus is on connection, subconsciously your perception of challenges and skills (being underwhelmed or overwhelmed in the dance) affects your ability to focus on connection in the dance.
When I interviewed Alex Krebs last year, he said he also experienced flow less often in comparison to his first year or two of learning. We talked a little bit about the concept of challenge vs. skills, and he agreed that may be a factor. It's definitely a complex and intangible thing to quantify, but if you are feeling like you are having difficulty connecting and experiencing flow in the dance, shifting your perception of challenge and skill may help. I read somewhere that our minds can only handle one or two challenges at once with any success, so for many it is helpful to be more focused and specific on what they are working on or focused on in the dance. I do this and have found great results and good peace of mind, and I recommend this to my students as well.
And unfortunately, Bordermantango, the flow research out there is mainly based on people's reports on their own experiences with flow, specifically in the realms of sports and art. I have not seen any research done to determine what is happening in the brain when flow is being experienced. I think research on Zen and the brain is your best bet because the idea with Zen is that its practitioners cultivate the ability to summon the experience through a set of techniques (for lack of a better word). Flow in sports and art (at least as reported by most) tends to happen without our being able to predict it or bring it about on our own. And the experience of flow is usually relatively rare, not an everyday occurrence. So I think that is the difficulty with trying to do research on what is happening in the brain during flow. But I am really curious to know! Perhaps someone who is intimately familiar with both Zen and dance flow can speak to how much the experiences are similar and whether the science of the brain should be comparable or not.