Even the best actors in the West End make mistakes from time to time. People fall, slip, come late to the stage, forget a prop, get the giggles, forget a line… the list goes on.
You might think that you’ve made the biggest blunder in theatre history, but it’s likely that no one in the audience had any idea! With this in mind, the number one piece of advice for on-stage mistakes is, keep going. Just keep going.
Never say “oops,” or any other explicative, because the audience probably has no idea you’ve messed up anyway. Even if they did, stay calm and be professional. If you have music in your performance, or you’re singing, try to memorize the music in measures or phrases so that you can easily jump back in at the right spot.
Sometimes audience members often enjoy mess-ups; it shows them that the performers are human. You must have the ability to fight through a defeatist mentality. Always believe in your capabilities as a performer! It’s in the nature of being human to mess up.