Specifically, the difference between the two.
They seem similar, but willpower seemed to be the mental push towards ones goal. Drive, usually against opposition, including, at times, yourself. But passion seemed to be emotional attraction to a desire. With passion, you don't need to be pushed, you are drawn in despite your will.
A person who can drive themselves towards something they sincerely desire is a profound force. It does not guarantee success, but I imagine they get far along their path. This might also be what some call flow or being in synch. I'm not exactly sure what would happen with the opposite. It seems more complex.
Even so, I imagine that while willpower contributes to flow, and can serve as an amplifier of it, it is not necessary for flow. The necessary element is passion or desire for the thing you want to do. However, willpower may be needed in order to keep yourself from recklessly destroying yourself pursuing your passion. As passion draws you in, you may be blind to obstacles and dangers in your path. Willpower checks your passion when necessary to ensure you don't run into a wall trying to get to something on the other side of it. Probably better to take the time to search for another way around, or make a way through it.
Of the two I suppose passion is the natural force- the fountain of initiative from which we are compelled to move. These are not the only compelling forces, though. Distinct from passion or will seems to be desperation. Willpower is something you can control. You cannot control passion. You don't decide what you are or are not passionate about. You discover what you are passionate about and make of it what you will. You can only use your conscious willpower to resist that instinctive passion. Likewise, you cannot control desperation. You can only deal with it when the situation comes about. Desperation compels you to act based on an imperative.
I couldn't work out whether some imperatives are actually consciously chosen, but nonetheless the sense of desperation for that imperative seems beyond ones control- only tempered with willpower.
These things interest me because I always wondered on the person and how we might not be a single whole. That in our lives we find ourselves negotiating with ourselves constantly- as if the entirety of me was a nation, but I am just on a council of influencers governing the body, parleying with urges, passions, lusts, desperation, fears, etc.
While it may seem being able to kill yourself is a testament of ultimate autonomy or authority over oneself, I do not believe this. In fact, I do not believe killing yourself to be a desire or oneself, but something one if pushed into by a passion or strong emotion or conviction.
Thus, I come to wonder who am I. And how am I different from the rest of what compromises me? Do I love, or does something tell me to love, and I simply move along with this feeling- internalizing and supplementing it?
Ah well...another moment of reflection.