The second point also sounds wise, but that first statement resonates very strongly with me. Allow me to share an anecdote...

One evening, back when I was learning C, I'd spent a hour or two reading Snow Crash by Neal Stephenson. Perhaps this primed my mind in some way for what followed. :)

I sat down and began coding... but my 'state of mind' was singular. I don't think I've ever been that focused. I began writing a routine to convert strings containing numbers in arbitrary bases to their numeric values... in Perl terms, this was a super oct().

I spent perhaps two hours total. My mind seemed very clear, and I thought through the problem in depth... I probably spent 20 minutes doing nothing but thinking between brief periods of typing. At the end - I hadn't yet heard of TDD, you see :) - I ran my code and started testing it. It worked the first time. Perfectly. Everything happened exactly as I expected. I made no changes to the code after that, because there were no more to make. My memory's a bit fuzzy, but I think I also had a routine to do the reverse operation, and that worked perfectly too. I was shocked.

I know I've improved since then and today I could probably find an edge case or two to break that code. But at the time, it was an amazing, almost transcendent experience. I couldn't believe I'd produced what I had.

So I concur - it's the biggest factor. This begs the question... What techniques do the monks have for 'focusing'? How do you enter 'deep hack mode'? Perhaps I should start a new thread. :)