I knew I was a mother when...
I picked my infant baby's nose with my bare fingers when no tissue was available.
I ate saliva-y left-overs without a second thought.
I held close a vomit-y boy when he was sick.
I wore my son's work-of-art pin/hat/etc. proudly in public.
And today, I knew I was a mother when I heard the words, "I hate you!" yelled at me during piano practice.