Hey, fellow failed entrepreneur here. My startup failed about 6-9 months ago. It was a very difficult time, our business partners went back on their promises and with that 3+ years of my life went down the drain. It was a terrible couple of months, lots of lost sleep, high blood pressure, I'm still dealing with it. I was unemployed for a couple of months, then finally took a job at a great company, where I feel great…
I agree with you about the only constant in life being change. I think it's even older than buddhism, I seem to recall it was Heraclitus who put it as "change is the only permanence".
As for the OP, I hope he stops taking losing investor money so personally. The investors knew well they bought a lottery ticket. Had OP succeeded, the investors would, of course, have gladly taken their part of that upside. Now, he didn't, and they lost their ticket money. And that's all it was: ticket money, their fee for getting to play the game. I sympathize with what he's going through, and hope he'll get through.