Ok, First I'll explain the comment. Throughout the book, the yang second line governing the lower trigram is often associated to a prince, while in the upper it is associated to a king. You know, lower is internal and upper is external. The king imposes his will to the world, while the prince just wishes he could, internally. That's how you fix the lower trigram on yourself, focusing on what you feel you wish you'd do it you could.
The receptive exterior (upper trigram) has a tension on the highest line, the abstract understanding of how things work and what's happening. When you get it all for being too open to it (yin) you're ready to make decisions, to define what to do to the world (become yang at the top). Hence the commentary on the 6th line.
These comments are often made to inspire. Even if you're not a prince, try to think big, as soon you'll have the power to do things the way you wish, and wisely, as you're supposed to, when making your decisions. For an ordinary person might as well use these same lines to do whatever they feel like, regardless of what's rational, even regardless to what is good for himself. The second line can be impulsive, self destructive, like the water, always trying to flow downward. And make decisions based solely upon your feelings is typically what stupid teenagers do. Hence the name of the 4th hexagram.
However, the change towards another hexagram is different than starting from it. The present is where your actions like, the future depends on how you do it. So it's the moment to define what you wish you'll do with the outcome of the trial. And beware of the risks of acting on a whim, that's how your energy will tend to be rearranged afterwards. There's been a lot of stupid princes as well.
And it doesn't mean you'll win. Remember that I Ching is built upon taoism, where life is a path to walk. Much later traditions in other parts of the world believed in fate, on access to what will happen because it's already written somewhere. Not a taoist, he believes the future doesn't exist yet and is being built and being changed every second. But you can change it too, anticipate risks and shape your future as long as you have enough power to. That's how the Oracle helps you. That's how it's been helping me for quite a while.
Best wishes,
Evandro.