The year I graduated from college, this used to be my schedule (I lived right next to my workplace):
8:30 AM - wake up
9:00 AM - go to work at corporate job
9:30 AM - arrive at work at corporate job
5:00 PM - stop working, go home
5:30 PM - arrive at home, run 3-4 miles
6:00 PM - start working on startup
2:00 AM - fight fires, go to sleep
Despite burning out a couple of times, I eventually got to the point where I could quit my job and work on my startup full-time. This didn't end up working out in the end, so it was a huge a waste of time (several YEARS).
At the end of the day, figure out whether your startup and your cofounders are worth the opportunity cost. Engineers can make a lot of money in this market working at FAANG (with a similar financial outcome as an acquihire exit for top talent).
This is controversial: Your startup should AT LEAST get accepted into YC -- that's the litmus test. If it can't even get past those relatively beatable odds, then it's certainly NOT worth it (YC acceptance de-risks things by a factor of 10 just purely based on statistics -- the partners are very smart, they are almost always right with their decision-making in terms of almost never having any false negatives -- but they still have 9/10 false positives, just statistically speaking). So if you DO get accepted into YC, draw the line at the one-year mark and make it firm. Return all the investors' money at that mark, and do something else (i.e. go work for Google).
That's how you know you are not one of the 9/10 failures that still somehow make it into YC. It's a good initial filter in that if you get rejected, you know right away that what you are currently doing is definitely NOT worth your time (and if you disagree, you are likely susceptible to Dunning-Kruger or self-bias -- you really should have been able to convince the partners that you were worth funding over the large pile of crappy applicants, otherwise, the HIGHLY likely scenario is that you do not realize yet why you will fail). For startup funding, the distribution itself is Pareto -- even the second best accelerator has a 10x lower rate of success (and often their successes ended up getting accepted to YC after-the-fact anyways). The VERY BEST investors' opinions are a good barometer for measuring startup success (BUT only if YOU are the founder -- otherwise, the reward portion of the risk-reward curve is below the Pareto Front).
If you can land a FAANG position, you'd have to start a unicorn on your own for it to be worth it (especially if you take in VC funding), so calibrate your success based on that. You can also adjust your risk-reward curve by joining late stage pre-IPO rocketships instead (Wealthfront has a list). Figure out where all the smart engineers are (they cluster) -- that's the winner you should pick. Even running a lifestyle business that generates similar income still probably isn't worth your time as a top engineer because of liquid stock appreciation from FAANG. Real talk: If you can't get accepted into FAANG, then you are in WAY over your head with starting your own unicorn (but doing a lifestyle business as a sole proprietor is probably financially optimal for you).
The absolute worst thing to do with your time is join someone else's early-stage startup with a significantly reduced salary as employee #1 for sweat equity (despite it being a fraction of what the founders have) and build their entire tech stack yourself. This isn't even close to being on the Pareto Front. Don't sell yourself short.
Also, you'll hear the story of that ONE exception who beat all of the odds. But you're a rational person, don't buy into that delusion.
This logic can be nicely collapsed into a probabilistic decision tree.