with little sleep now
I'm not the preachy type, and I'm not going to tell you how to live your life. But I will share this observation from my own life. If I read my other post, you'll see a part where I say "I had a heart attack". OK, at the end of the day, nobody can really say exactly when a given person has a heart attack on a specific day. There are various risk factors that contribute, ranging from age, to whether you smoke or not, to stress levels, to weight, diet, etc., etc.
In my case, I was a bit overweight, but had otherwise been fairly healthy, and I was only 41 at the time. I had no near relatives who'd had similar issues, etc., so I had very little inclination to think I was at risk of something like that happening.
But what I was doing was working like 80+ hours a week between the day job and the startup, drinking ridiculous amounts of coffee / red bull / etc., eating chocolate covered espresso beans on top of that, and struggling to get by on not-even-close to enough sleep.
Did all of that contribute to my having a heart attack when I did? It's hard to say for sure, but it's pretty well established that failing to get enough sleep is a major health hazard... and doing in in conjunction with borderline OD'ing on caffeine probably just makes it worse.
So yeah... not going to tell you anything about what you should or should not do. It's your life and your priorities and values. Just please be consciously aware of the risks of certain behaviors and take those into account. That's all I can really offer.