Busy Teachers need an escape valve, a way to handle things when the disruptions get out of hand. This means you need to have X-Time available. X-Time is time that you put in your Weekly Plan at the start of the year; time outside school which is earmarked as an 'emergency' slot for doing extra work. In the ideal world, it will not get used regularly. If it is getting used regularly, this gives you a clear clue that something is wrong.
If you are following the magpieplanning method, you will also have BBL2 (this stands for Best Bad Lesson). These are pre-prepared lessons that you can roll out when you don't have time to plan and prepare.
Of course any escape route can become a trap, and you need to be disciplined in making sure that you are not using your X-Time routinely, or using up all your 'lazy' lessons too quickly.