Where the previous sign, Determination, is associated with strong action based on the dual force of conviction and circumstance, this is (as careful readers might note by looking at the signs themselves) the opposite of that. Opposite, in terms of the I Ching, does not however mean the mere negation of what it opposes. Pure force means it is time to step in and/or up; pure change means it is time to step back. The difference is stark, subtle, and important.
An example of flow can be seen first hand when visiting a theatre where preparations to put up a play are in full swing. There are a myriad of people doing a gazillion things, each of which are very specific, very urgent and very dependent on everyone else getting their particular thing right. Everyone is super busy, and everyone directly involved in the production is in a state of controlled panic (which, indeed, is a state of pure force). You as a visitor, however, are not a part of this frantic activity, and more often than not your role in this situation is to shut up as much as possible, and step out of the way as props with varying degrees of intuitive obviousness are carted by.
The proper way to act in such a situation is to realize that nothing there is about you. You are not important in this situation. You are, however, able to contribute meaningfully to the outcome of the process if you apply the proper attitude of humbleness. There will inevitably be heavy objects in need of bodies to carry them, and you – as a body who does not do anything immediately important – can help out by playing the part of carrying. The nature of the objects carried does not matter, and even if it did you are not the one to have opinions on the subject; all that matters is the work and getting it done in time. The proper thing to do is to roll up your sleeves and, following the (probably yelled) instructions to the letter, dig in.
The same principle carries over to other contexts, where flows are occurring and the possibility of changing their trajectory is negligible. When attending a wedding, for instance, the key thing to do is to not step up and accept the vows on behalf of the happy couple; the winning move is to sit down and let it all unfold as per ceremony. This is not mere passive attendance, however; being an audience member is an energetic activity in its own right. Think of happily crying grandmothers, who are at once heavily engaged in the process and yet do not prevent it from proceeding; they embody this mood.
Flow is also the sign associated with creativity within constraints. From what you have read above, it should come as no surprise that accepting the limitations and working within them is very much the proscribed thing. To quote: a line becomes a rectangle becomes a cube. The creative change is not brought about by altering the rules, but by following them to their logical conclusion. The move from one to three dimensions comes from going with the flow inherent in the principle of the humble line.
If something is going to happen anyway, the proper thing to do is to is to accept the situation and act accordingly. Sometimes, this means playing along. At other times, this means subverting the rules by following them. At yet other times, it’s matchmaking: bring two powerful forces together, then back away and allow them to interact on their own terms. At all times, the key words are humility, acceptance and discretion.