It’s interesting because I think the theory explains that the cause as to why. For instance, relationships can either produce flow or they can produce anxiety or boredom. If the person seems out of control and very strange or too wrapped up in himself, you don’t want to interact with that person too much just whatever is necessary. Or if the person is so predictable and routine and the way they think or talk then again, it’s boring. Flow comes when the person is interesting, challenging in a way but not too much in the sense of you want to understand it. You want to somehow interact and find a common ground and explore together what happens in life and with each other relationship-wise and that's interesting. The challenge motivates you to try yourself to be better, to be sharing or understanding in response to the other person so that we can both discover and meet a common challenge and that becomes a relationship that could grow instead of just being stagnant or chaotic.