These things happen

'These things happen' is used to tell somebody not to worry about something, such as a mistake or accident.

Examples

• Person A: "I'm so sorry for spilling coffee on you!" Person B: "Don't worry. These things happen."
• Person A: "I can't believe I deleted that file!" Person B: "Look, these things happen. Don't beat yourself up about it."
• It was disappointing not to get that promotion, but these things happen. I just need to stay positive.