My dad used to put it really well - He used to say (when my own two would rather speak to my mum, their nan, about certain things rather than me....)
He used to say "well your the profit in your own home".
Meaning, as I am merely "mum" who obviously knows nothing, what ever I say is rubbish. Where as my mum, well, she was the source of ALL wisdom.
But now I am the nan, my step grandchildren, now ask my advice!
So, putting it simply - Being great is being the one your grandchildren can speak to about any awkward conversation, rather than mum or dad. 