Unless you're asocial or firmly entrenched in a rut, there will always be things that get in the way of your routine. You just have to adapt.
Reminds me of the storm duty I worked on. Worked for 28 hours straight, got a workout in, ate some eggs and some oatmeal, and then slept.
If I had a friend that I hadn't seen for a while (moved away, military, etc.) and they were coming in on Saturday where my cheat day was a Sunday, do you think I said, "Oh gee, I can't go to your barbecue and drink until tomorrow!" No, I ate and drank and went a whole week before the next cheat day.
Stuff like that. Things will pop up - if you're motivated enough, you'll find a way to stay on track without compromising your work or social lives.