which would be a....... that u will regret the most in your life?

I regret one mistake which can now never be corrected.It was my son's first birthday and my mom and me had prepared a meal for everyone.Guests had arrived and we were just starting towards the ritual of cutting the cake.My mother told me its getting late I think you should cut the cake.I said okay and holding my son I moved towards the cake table thinking my nother was behind me.Infact on her way she had turned towards the temple to get somthings to bless my son,the hindu way.I didn't realise that and on everyone's urging,I just lit the candles and posing for the camera we just cut the cake.Later on my mom told me why I didn't wait for her to catch up.I realised my mistake I should have actually asked her to hold my son's hand to cut the cake as we normally do in all the celebrations of the kids at home.Grandparents help the kid to cut the cake.I thought okay from next birhday I will make sure she will help him cut the cake.But unfortunately my mother expired after 5 months due to massive heart attack and I could never correct the mistake I had made.I will regret it my whole life and I miss her on all Birthdays I celebrate.