When my daughter and girlfriend go to bed and I get half an hour just to sit quietly with a coffee and watch TV, read a book or the like.
The natural high when you finish a long run and are near the point of exhaustion.
My daughters beaming smile when I get in from work every night and you realise someone is genuinely delighted to see you. Also her ridiculous uncontrollable laugh when I blow raspberries on her stomach.
When the cat climbs up on my knee, curls up and starts purring away contentedly.
Having a big bag of M&Ms when no one else is around and being able to eat the whole pack without sharing them.