I'm asking, I seriously don't know.
If you came here for an answer wrapped with a bow, I'm sorry, but you won't find it. While I haven't found it and I'm not even sure I would know it if I stepped in it, what I have discovered thus far in my search is that it is not a thing. It is not a: person, place, job, title, bank account, lifestyle, hobby, or any of the other dozen or so places I've looked.
It would seem that a passion is in porn terms; what gets you off.
The thing about it is that there can be many things that get you off and those things may change over the years. It is situational, but not necessarily a sum of its parts. Passion can be a bit of moving target in that respect. The high you get from doing something, that dopamine response, is what I believe to be an indicator of one of your passions. It isn't so much the thing you're doing, as it is how doing that thing makes you feel. However, doing other things can also make you feel the same way. This is where is gets interesting and hard.
You might notice that you like working with people and helping them and decide to volunteer at a community center. This may, at first, seem to be the perfect fit for you and that you have found and are actively working in your passion. But over time, things change. You can't quite put your finger on it. You're helping people and that used to be enough and now it isn't. That's the problem with Dopamine, it's a drug, and like any drug you need more of it to get that initial high.
Or you just need more doses in shorter instances.
Perhaps helping people isn't actually your passion? Maybe if you analyze what it is specifically that you liked about working with people you might find something else was hiding in the weeds. In the beginning, helping may have meant teaching. As time went on, there was less of this. If you examine the down time to see where the spikes occurred, you might find out that when you really got energy from helping was when you were helping by teaching. This doesn't mean you should become a teacher; it just means that you leveled up. You sharpened a finer point. Narrowed things down a bit to identify what it is more specifically that gets you off.
Equating passion with money is probably not the place to start. I don't believe that assigning a financial value here works because it can too easily take focus away from what is important and lead to misdirection. The payoff I'm looking for is not something that can be valued in terms of money. It's more than that. Chasing the money as I and many have found doesn't lead to fulfillment and is usually temporary. The money sooner or later will not be enough. Much like a relationship based on sex and physical attraction, eventually you get old and saggy and there better be something else supporting the relationship or it will evaporate.
Be aware of dopamine distractions as well. It comes in many forms and can just as easily misdirect you as money can. I've found that if there is an element to the dopamine fix that also energizes you, this might be an indication that this particular source is more potent and true than for example a "like" on social media.
So that's all I got for now. It's what I've managed to learn since I've been researching this and going through it personally. No answers, just more questions it would seem, but hopefully some clarity. I find that being able to name or define a problem is the first step in trying to figure out a solution. One more thing, passion may not be related to creativity or humanity. Most things out there point in one of these two directions and I'm not convinced that they are the only options. We need more than artists and humanitarians. Though I wonde