One of the biggest problems with exceptions is how easily they can ruin your schedule for several days after, making them not feel worth it. They become much more viable if their impact can be reduced.
Recovery processes are a very effective way to snap back quickly after an exception. These should restore sleep, diet and exercise to regain energy, and quickly rebuild any habits that were lost. A good set of recovery processes should be able to fully restore a Friday exception by Sunday morning.
For exceptions that last longer, like a holiday, it’s more likely that several good habits will get fully broken. This is when it may be useful to temporarily restore banked systems that worked in the past, making it much easier to build back the habit.