Well, there is no one answer, its really down to you.
Personally I would look at all the things I had done and learnt over the time and work out what is actually useful.
Take a recording device (iphone recorder will do) and talk into it "the good, the bad and the ugly".
Be honest with yourself. Everything thats been floating around in your head, all the things you did wrong, all the opportunities missed and lost, the things you did get right.
The time you did the wrong thing by the client, by the supplier, by your partner, how that made them feel ... the works.
This can take one session it can take weeks of 5 minutes a day. Until you get it all out.
This allows you to acknoweldge all the feelings, guilt and worries and allows you to move on.
Then evaluate "knowing all I know, do I really want to try again?"
What out of all of that learning can I take and use? who do I have to apologize to?
If you decide to move on and try again, then what am I going to do different in the next 12 months to the previous 12 months?
What is my new short term (2 week to 2 month) definition of success? Get a few early wins, what ever they are, it doesn't have to be money, it can be new website, new product/service, new sale, new business plan ... something to talk about as a success.
From this you can point to a change and point to a success happening from that change, this is key when talking to others who tell you to get a real job. You build yourself back up and build the story in your head back up to match it.
and listen to Newton Faulkner - Long Shot ... it speaks to me about this.