I'm in a similar boat, except I have 10 years on top of yours. It's actually been a lot of fun, the learning and building, but I've been driven by the same fear.
First off, this is hard and very few (any?) have this figured out. It took me going through a major depression episode and other, significant, life changes to start to work on this.
About a year ago I've started to change some key habits and that has helped to alleviate this feeling. To start with:
* Reduced the amount of tech news / startup news I consume significantly. I cut down the number of blogs from ~ 300 to ~ 10.
* I have a hobby (woodworking in my case). I tried a bunch of hobbies over the years and it took a while to find something that I'm sticking with, but just keep experimenting
* Meditation and non-tech and non-business reading has helped. Instead of reading 10 business/startup/tech books for every 1 fiction/biography/history/fun-topic, I reversed that relationship.
* Vacations. Not some huge travel-the-world stuff, but a weekend getaway with friends / significant other is amazing. Could just be to look at vintage stores, art galleries, sit on your butt by the pool, etc. Don't have goals, get lost and don't watch the clock
Lastly, the most important piece. Spend the time and the energy you're investing right now in projects and "growing" on figuring out what you want out of life. This is not some existential thing nor is it some grand plan. Starting a company is a goal and good one. Traveling 3 months out of a year is a goal too. Don't get hung up on it, it'll change and evolve over the years. Just start somewhere, you can "pivot" as you move forward.
Here's the most important piece though - how do you measure yourself? Forget realistic/unrealistic or external/internal - doesn't matter. Identify what are the metrics that you use to gauge your progress and what it means for you to have had a successful week (day - too short & month/year - too long).
Then, ask yourself: why that?
The answers to the questions above will help show you a path from feeling like you're spinning in one spot and what to do next.
Reach out if you want to talk about any of it.