I thought that I knew it - but - I have learnt a long time ago that things are not the same upon refection and comparison to recent knowledge.
My favorite anecdote;
Mr Einstein, what is your 'phone number? I don't know? But I thought you were a brilliant scientist and you knew everything? Aaawwww, I know where to find it.
No-one can know everything - my Degree told me that. But the knowledge that you can either look-up the answer or deduce it from first principles, tells me that we can learn anything if we want to.
You sometimes need the right motivation.
Cause all of the stars, Have faded away, Just try not to worry, You'll see them someday. Take what you need, And be on your way and, Stop crying your heart out.
