Please, please, please don't let yourself get into this way of thinking. Diabetes is a hard enough condition to deal with without feeling that you need to be perfect. You can do things the same way from one day to the next, and not get the same results. I've had days, even as a T2, where I'll eat a meal and dose for it and I'll do just fine. Eat the leftovers the next day and dose for it, and I go low or high. T1 is even more volatile, and we're all human, with human fallibility. The trick to avoiding "complete derailment" is to simply do the best you can, and accept that there's going to be some missteps and detours along the way, and to manage them as best you can as much of the time as you can.
I was reading this article in Huffington Post this morning. There's a lot of anxiety that comes along with dealing with diabetes, a lot of judgement about us being "in control" of it that really shouldn't be there. Really, we're just doing the best we can, juggling flaming chainsaws whilst jumping on a trampoline some days and still trying to keep up with the rest of life as well. We're only human. Some days we forget our keys and have to go back just like everyone else, and some days we forget our medications, just like everyone else out there who takes a prescription.