How good do you have to be? Better than you are, clearly
I know flaking is a bitch and it will happen to the best of us, it's just human nature. This is why maximum closes per week is essential. If you work on the assumption that maybe a third of your closes will not flake, that means you need three solid closes a week to have an option of one single day 2 for that week.
There's an old Mystery post from back when where he breaks down the numbers of his pickups, how many follow through etc. It's a good read.
You need to accept flaking WILL happen, but you CAN reduce it.
If you post a couple examples of flakes you've had happen, what led up to it etc. I'm sure I could help you out a little bit, as this is an area I've recently worked on myself.