As rone said, mental toughness is what it's about. Just don't give in. If you're already saying to yourself that you're not going to finish then my guess is you wont.
Riding with someone is good, but don't rely on it. During last years race I started out riding with Miketually lost him around 30 miles, had a period alone, joined up with a total stranger who I to'ed an fro'ed with over the next 20, had another period alone, met said stranger again for 5 more etc, etc.
Can't see there being as many lonely stretches with so many more riders this year.
There's a down side to riding with someone too. I discovered in my two previous 12hr races that negativity can be infectious. I found myself riding with people hating the conditions and talking about quitting and my mind starts to think the same. Once away from them I focused on not quitting and just keeping riding.