from a friend -
In my 20s I KNEW I KNEW everything.
In my 30s I realized I KNEW nothing.
In my 40s I KNEW what I KNEW and I KNEW what I did not KNOW.
In my 50s I KNEW no one KNEW what they were talking about.
In my 60s I realized the grumpy old man I was scared of becoming - KNEW it all along.