Hi!
On the whole, most people are putting more glucose into their body over the festive period instead of less. Many people understandably think they can wing it from once mince pie to the next so long as their meter doesn’t blow up, unaware that they’re slowly restocking glucose and thus directly increasing any insulin resistance that they may already have, resulting in wayward control some days later. Seen it myself a million times and read about it in detail. I call it the elastic effect but it’s really the glucose overflow that Jason Fung promotes. Or rather that’s the hypothesis which I happen to agree with based on my own knowledge and experience.
Without knowing more about your condition, and management of it, it’s not sensible to offer advice on the most efficient way to get back to ‘normal’, particularly as you're an insulin user.