Burnout (now officially a medical condition!) can come from doing work you don't enjoy, having vague goals or not having strong enough social support. It also can come from doing exactly what you want.
The challenge with burnout isn't always what you do, but how you do it.
Do you still need to do it?
One of the quickest way to burnout is to not create repeatable systems. It may make sense to learn to code, produce and market your product to get it off the ground, but at a certain point, your skillset doesn't scale. Can you imagine Mark Zuckerberg still editing each programming line of Facebook?
Instead, it makes more sense to offload your previous obligations to make proper room for future priorities. I use a social media manager to share my posts, allowing me to focus on coaching, speaking and writing. I could see myself burning out on social media responses and interactions - not because they weren't fruitful, but because I've been successful enough to have social media followers.
Then, why am I still doing it?
A precursor to a success-driven burnout is micromanagement. It is the small pizza shop owner who must make every batch of dough herself, even when her pizza parlor has expanded to two dozen locations. It is the founder who still must decide on every single action, even when his bootstrapped startup is a million-dollar company.
Creating a system will help you stave burnout, but you'll only seek out a system when you're self-aware to realize that you've grown.
When I've talked to people fresh off a burnout, they almost always say the same thing: "Why did I have to do all those little things myself? It doesn't even make sense."
Unfortunately, it's easy to take a well-regarded company or a profitable business as a symbol that you are doing everything right. It may be half-true: You did everything right to get to this point, but what got you here won't get you further.