In this case the thing is whatever you want to happen. Maybe it’s recording a great performance, or writing a song, or even just being the best you possibly can at anything. So you prepare, and then you turn the part of your mind off that’s always watching and criticizing. Because that shit us guaranteed to keep the thing from showing up. The thing requires that you be completely relaxed and in the moment.
You can’t force it – but you can set the stage and maximize the chance it will show up. And when it does, it’s fucking magic.