I've had a few bad nights, am I going backwards?

The odd, bad night's sleep can actually be really good to reset your sleep cycle.

Because your body is so efficient at recovering and if you keep your behavior the same, it can actually reinforce a really good routine. Seeing a bad night's sleep as the worst thing in the world is actually not that helpful.

Can I cheat on my sleep scheduling?

"So what if I'm 89% sleep efficient or what if I've had two bad nights and five good nights during that week? Can I not just take away the bad nights and only calculate my sleep efficiency based on the good nights?" Well, of course that will look really good on paper and you'll be able to increase your numbers and it will look really great. But unfortunately in reality, the reason that we have set out the way that we have is because in research, that is the amount of time you need for your body to get used to everything.