Listen earnestly to anything your children want to tell you, no matter what. If you don't listen eagerly to the little stuff when they are little, they won't tell you the big stuff when they are big. Because to them it was always big stuff.
I agree children need discipline but people get so judgmental and mad when a three year old is having a bad day. Your kids weren't perfect and neither are any one else's! So stop judging a parents parenting based off a one time meeting.