I've learned to decipher kids cries. Where I used to get angry and annoyed at children crying, I now hear 'tired', 'hungry', 'cranky', 'overwhelmed', sadly sometimes 'scared', and even 'spoiled' and feel sympathy.
I've learned that if you see kids at the grocery store in pajamas and it is one in the afternoon, don't assume that they've been in those pajamas all day. Their current ensemble is likely the fifth of the day.
I've learned that if you see a mom in pajamas at the grocery store with three kids in tow and it is one in the afternoon, it is safe to assume that she's been in those pajamas all day. For this reason, please be kind.
I've learned that if you see a mom at the store with what is obviously children's jewelry or with a hairstyle that is obviously contributed to by children, smile at her but don't mention the unusual hairdo. Please. She has forgotten that she let her kids fix her hair and dress her up and reminding her that she is still 'the prettiest pincess in awl of da house' might make her realize that the man she thought was checking her out when he smiled at her was really just smiling because he thought she was ... well, she might just keep thinking he was checking her out because she needs to feel attractive that day.
I've realized a certain pride in knowing other humans so intimately. Identifying little voices on the phone that sound like any generic toddler to the uninformed, telling sleeping children apart by their breathing, knowing who's coming down the hallway by the footsteps you hear. Being able to tell who passed gas by the smell of the gas, though - that's a certain intimacy I could do without. I nearly cried when I realized I had climbed to that level, but then I laughed, while holding my nose. And then I stopped laughing because the smell was so bad that even having an open mouth was not acceptable.