The phrase ‘let bygones be bygones’ means to forgive and forget past disagreements or problems. It implies moving on from past conflicts instead of holding grudges or dwelling on old issues.
This expression is often used to encourage reconciliation between people who may have had a falling out. Instead of allowing past mistakes or arguments to affect the present relationship, the phrase suggests that both parties should acknowledge what happened but choose to leave it in the past.
For example, if two friends had a serious disagreement, one might say, ‘Let’s let bygones be bygones and focus on enjoying our time together again.’ This shows a willingness to move forward and restore the friendship without being stuck in the past.