How do you manage to do all the things you want to do?

That's the neat part, you don't!

Don’t have kids haha.

I don’t. I have to prioritize them.

Which I avoid doing.

So basically, I do none of them.

I don't.
I don't have kids, I work 40hrs a week, I don't buy little things I want because there's a few "big" things I want that'll I'll need about $800 for.
I make it almost paycheck to paycheck and it will take me at least 6 months to save $800 if I buy nothing else.

I quit work at 35 because there are so many things I wanted to do, and.paid work wasn't one of them, am now 58.

Alas now there are just more things I want to do.

I don't.

You won't be able to, narrow your focus to 2 or 3 things at a time. If you lose interest, try something else.

"That's the neat part, you don't!"

Actual answer, ya gotta learn to prioritize what you can manage at any one time, otherwise you're gonna bury yourself under the weight of mounting project pressure.

My boss and I wanted to do some fancy data formatting shenanigans this year, but I've fallen sick enough that we gotta backburner it until I can get back at full capacity.

One piece of advice I can offer (as someone with a similar wide range of interests) is that you should sometimes treat life like a field trip. If you meet an expert in something, ask questions and show enthusiasm. Experts (usually) love talking about their favorite topic. I know a gearhead who restores old cars who doesn’t talk much. But if I ask about any car, he will put his beer down and talk about different cars until the sun comes up. Chefs love talking about food. Most people like telling people about their life’s work (as long as you aren’t the type of asshole who tries to tell a Ph D they’re wrong because someone on the internet said something else).

Also, people say life is short. It’s actually simultaneously too short and too long. You won’t have time to be a Ph D level expert in all your interests but you’ll (hopefully) have decades to learn about whatever floats your boat. Life can get in the way but if you find hobbies you like, it’s restorative. Work and family responsibilities exist, to be sure, and lots of people feel too drained for hobbies but doing something fun isn’t draining.

I don't. Or more accurately, I focus on what makes money so we can survive, and dabble in the other interests.

So in your example - become a psychologist, and just stay interested in the other stuff. Travel and learn about archaeology. Read and learn about zoomorphology, learn to draw and do illustrations, sell them as your side hustle. Do cosplay and be critical of the wardrobes in historical dramas. Use your other interests to enrich your life to the extent you can manage to enjoy at a pace you find best. And be mindful, don't always focus on what you can't do, be present in your life, live it.

Pick the most lucrative and least likely to result in burn out as a job. Read, watch, travel to learn about and/or experience the others. Most people have interests outside of their jobs. I work in healthcare and i like to learn about new things in that area, but i also spend a lot of time on gardening, cooking, crochet, cannabis, and cute animal videos.

By being overwhelmed and not doing them all.

Or take meds and follow the daily and weekly planning I make every sunday.

I don't. At some point, you've got to prioritize.

I like the advice others have given, particularly the "no kids" suggestion. If one of your core interests is raising kids, of course, you're in for a wild ride. But if raising kids isn't one of your core interests, then give it a good long think. There's no rule that says you have to have kids. I'm in my mid 50's, happily married, never had kids and it was a great decision. Zero regrets. Leading a full life.

I also suggest taking a long-term perspective when you're trying to balance how you use your time. The circumstances of your life are going to hinder and enable all your interests in various ways over your life. Lean into that. There are core interests of mine that I've shelved for years at a time only to later revisit in a new way when my priorities re-aligned.

On the long run, it's all been balanced.

It's great you're thinking about these things. The unexamined life is not worth living (said Socrates). But please don't feel overwhelmed. The great thing about this dilemma is that you're the one who gets to decide if it works out in the end.

Ill tell you if I ever do all the things I have to do on time.

For a long time I tried, but one day I just decided to focus on the hobbies I care the most about. I dumped a lot of time into software for my career, then kept up with bass guitar practice and dirt biking. All the other hobbies are things I might pick up if I have a surplus of time, but I've accepted that I'll never go that deep into them.

I dont do anything. That's it.

It's easy when you don't want to do anything.

I just find ways to combine them all and multi-task whenever possible.

So if you are in school or going back to school for psychology then I recommend just focusing on your degree and maybe take elective classes in your side interests when you have time. I didn't study psychology but my major was really labor intensive and I needed all the time I could to study and work on projects. However, I did take a fun forensics class as an elective that is still one of my all time favorite classes since I loved CSI.

After you graduate and get a steady job, you'll have more time to focus on your interests. I schedule out my week and take classes at a local school after work in things that interest me. Then weekends I dedicate to family/friend time. I also watch YouTube videos in my free time.

As many people have mentioned kids, its good to note that I don't have kids at this time. I plan to have kids in the future and am aware that my night classes will have to end when I do. However that's a sacrifice I'm willing to make because I really want kids. I just hope that one day I'll be able to share my hobbies with future kids or enjoy what hobbies they are interested in.