Firstly, your issue doesn't seem to be anything other than social anxiety
If you have to 'lose sleep' after contacting someone on LinkedIn about your product, then you are just not suited to doing a startup
Secondly, there is nothing to feel bad about
Vast majority of people are not suited to starting a company or working in a small startup
Lots of good jobs in middle and large companies for you
Thirdly, the scale of stuff you are talking about is miniscule
I walked away from a Green Card to start my company
If I didn't succeed, I would have lost access to the developed world FOREVER
You are upset that your girlfriend had to stay at home one year and you couldn't take her out for dinner????
Finally, this is a Catch 22 situation. Not sure why you are submitting this or writing about your experience if the ENTIRE reason you quit was you couldn't handle doing sales and marketing and putting yourself out there
I'm reluctant to respond because people who have social anxiety can sometimes take genuine feedback and mis-interpret it
What I'm trying to say is that the extent of the risk you took is not very high
And the reason that stuff didn't work out is your social anxiety
So just make sure you don't take the wrong feedback from what life is telling you