Try lots of things, see if something sticks, it might take years, or decades, but the variety of trying many things is interesting in itself.

Try to connect the dots in your own life, for example what were you like as a kid, what interested you, has any of this followed into your adult life, what about looking forwards e.g. where do you want to be 30 years from now and can your current or new interests get you there.

Having kids will certainly give a person purpose and eat up all of that free time if that's in the plan for you.

The answer is already in your question: Find the reason you don't have energy.

I didn't find my complement, but didn't mingle widely until later on, when jobs put me in contact with many.

A friend I met after changing coasts liked trains, but it was a good excuse to carpool to fishing locations near those lines. I couldn't fish worth a damn, but those were beautiful locations, and they revived my photographic bug.

Things do connect, but not in isolation. Hobbies, either by association, or just getting out, create opportunities.

My focus isn't "me": what am I passionate about. My focus is the "other": how can I help a few people a lot, or a lot of people a little.

So, for me I do not try to find my passion first. I try to pick something small that helps someone. Energy will follow.

The nature of work also combines passionate with non-passionate stuff. We may love writing high quality code, but most of the day requires hacky low quality code, meetings, or digging through documentation. Or part of a pipeline of gathering, cleaning, and selling data to a financial institution that uses it for medium interest loans.

The better measurement is find out what work energizes you. You might not feel any flow or fun. You might not feel any emotion whatsoever. But you get out of it like a good workout - both tired and energized.

For instance I didn't really care about football until someone explained all sorts of details about the game to me.

You can also develop that appreciation by doing things. The more art I make, the more art I like. I had a brief and unsuccessful woodworking phase that makes me stop when I see nice joinery or beautiful furniture. Years of reading about plants and smelling flowers made my forest walks slower and much richer.

So I guess be curious? Seek a deeper understanding of many different things.

Do with that information what you will, but it might be that you are looking at passion wrongly, expecting to 'find' something you are magically passionate about.

Beyond that, take care of your health, rest and play around with things to increase your surface area of finding something that works.

Thinking about this has become an endless source of misery for me. Still, every day I take on some challenging work and start working on it, whether it interests me or not. If it does not, I switch. If the next thing does not work, I try harder again.

I have also started talking to more people and trying to find a group of highly ambitious people. One thing I have noticed about people who have succeeded is that they nailed two things. First, they found a direction. Second, they found an ambitious group that acted as an engine for them.

Time does not matter as much as direction does.

Then, are you looking for something that you are already passionate about, but are unaware that you are? Or are you looking to discover something to become passionate about?

Either way, talk to people - people at work, neighbors, people at church or the bar or the gym or the park. What were you talking about when you suddenly realized that you'd been talking for 45 minutes? You're pretty interested in that. Or, what was the other person talking about for 45 minutes, and you weren't searching for some kind of graceful way to get out of the conversation? You're pretty interested in that, too.