Founding engineers and early employees: what really is our mental model? I will not promote

I see a lot of motivational content and practical advice for founders here and everywhere online about grit and perseverance and how you'll make it eventually. Advice about how you shouldn't work for someone else but yourself, yada, yada. On the other hand I also see a lot of advice for employees at large companies to try and move to better roles every few years and build their career, how attachment and commitment to a company is not good, not to work overtime for no pay, or alternatively go and start a company. What about very early employees at a startup? What should their (our) mental model be? The grind is very real. No sleep, barely any weekends, average pay, all because you believe in a vision. But even if it pans out in a couple of years, you get almost nothing. 0.1% equity is considered generous and that gets diluted down. Yes you learn a lot but leveraging that up for your next job should you decide to leave in a few years is practically hard because of the no-name company on your resume. Honestly, I can't find this community anywhere I look. It's all either founders who are fully attached to their company like their baby or employees who are completely detached from the big corporations they work at. How about the people who ARE attached to the company they are building but are not founders? I can't find books or anything like that. It's all about building YOUR company, YOUR product. But what if you do feel like it's yours and it exists because you played a key role, but it's not yours at the end of the day?