The truth about filmmaking is you have all these ideas and you're trying to convince everybody that they should buy into this idea, but at two o'clock in the morning when you're all on your own you're going, 'Geez, I hope I know what I'm doing. I hope this idea is gonna work.'

This quote is about the filmmaking process. It is saying that when coming up with ideas for a film, the filmmaker often has to try and convince other people to believe in and support their idea. However, when everyone has gone and the filmmaker is on their own in the middle of the night, the filmmaker can start to worry and doubt themselves, hoping that their idea will work out.