I am so sorry you feel bad. Want some advice from an older engineer turned entrepreneur? Be proud of what you have done. Not many people take risks in life. You did. Being the 'man in the arena' is enough. I read this quote from Teddy Roosevelt often:
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat."
I'm going through something similar to the OP, I haven't given up yet and don't really consider it either. But, it's really hard. My mental health certainly took a hit and I'm full of anxiety as my savings are not enough to cover the upcoming bills and couldn't find a contracting gig so far to support the cashflow. I've experienced severe panic attacks and bouts of depression. I sometimes dread the passing of days.
Hope I'll find a way.
It might be illogical to say this but I know we'll make it one way or another. I believe in what we are doing and what we built actually resonated with the customers as well. Just need to power through this last mile somehow.
Anyway, reading your comment gave me a little more strength. Much appreciated.
I have had anxiety/depression too my whole life. Took me years to understand it and figure out a path forward. Therapy, meds helped a lot. And it took me decades to get the skill and perspective to start a company. Life is pretty long, if you spend 5-10 years dealing with depression -- you still have a 30 years of work to try new things once you learn to deal with your biology!
TBH that's a perspective I did not have. At 27 years old I feel like I've been slow and like I'm late for some of the aspirations I've had. I tend to look at things from a daily perspective. Today and tomorrow.
Thinking in decades however, reframes and somewhat changes the problems. I'll keep this in mind.
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat."