Which has been the happiest day of your life?

Once I was working with Doctors to get light weight Floor Reaction Orthosis (FROs) for polio affected persons. After taking the measurements when the children were fitted with light weight FROs weighing 1/10th of the original weight which they were carrying, the children started running, walking and pedaling cycles. Their mobility brought tears of joy in the eyes of their parents. The sight of happiness on their faces brought bliss to me.