Understanding that people have invisible walls that must be broached before a tango connection can be established is an equation that is just as hard to solve as any mathematical formula.
As a person who has many walls of his own, I know that the most difficult problem is acknowledging their existence.
My biggest wall was my fear of arousal. I took it down by convincing myself that tango would never lead to any close encounters of the sexual kind. It was almost like a vow of celibacy.
Some walls have to be torn down by the occupant behind the wall. Some walls have to be taken down by the intruder.
I have to imagine that performance anxiety is the most common barrier encountered by partners in this dance. It can be surmounted by letting a person know that he/she can never make a mistake; that you are completely aware that this engagement is an attempt to choreograph movement to a song spontaneously and that turbulence is to be expected.
It takes two to tango. If you want to dance, it is imperative that you let someone else into your space: physical, mental and emotional. You must leave your expectations for success and your fear of failure behind. In tango, there are no penalties or rewards; there is only the music and the next step.