When you are in an emotional low, it's very difficult to think, "I should just persist because PG says it usually works."
I usually take the opposite approach: I should persist because PG says that single-founder startups don't work, and I'm going to prove him wrong, damnit.
Good for you!
But in my experience, 1+1 is MUCH greater than 2. If I'm right 99% of the time, the other guy has hauled his own weight just by correcting me that 1% - because I'd have been blocked, or gone the wrong way, or dropped a ball. And there are 99 decisions to make every week.
There are a lot of explanations why one is not enough. Think about practicing a foreign language - how it's much better when you have someone to talk to. That's also correct for almost any kind of evolving processes. Even a reading (which is a classical example of a lonely activity) could do better if you will develop the habit of reading aloud, like Tibetan and many other cultures have.
I wonder though, with the comments about how the character and commitment of your co-founders matters so much more than ability or output that, in the case you can't get someone you know well to join you, that you would do better not having a co-founder rather than spending time looking for one.
I usually take the opposite approach: I should persist because PG says that single-founder startups don't work, and I'm going to prove him wrong, damnit.