Let bygones be bygones is an everyday proverbial expression which means to forget any wrong doings of the past.
The main motto behind this saying is to forgive and forget. It means to let go of any past grievances or mutually agree to forget any quarrelsome issues of the past. It is like making amends and starting afresh.
It implies that whatever is done is done and is best forgotten.
1. Sumit and Ram decided to let bygones be bygones after not having spoken with each other for a month.
2. Mr. Sharma decided to let bygones be bygones and organized a surprise party for his estranged wife.
3. My friend wished that his neighbor would let bygones be bygones and start speaking to him again.