that you are seriously deluded as to how old you look 
My school are having a reunion for my year in June - it's been 23 years since I left school - all the people who have signed up to go I recognise the names but they all look ancient! Short, old-lady hair, too much lipstick, giant 'pissed at 40' smiles 
That's what I look like and I just don't know it right???
I'm wondering if I should go - Home Counties back to 'Wickerman' country. 