Or what makes a day great?
As a theoretical construction would take ages, I’d try an empirical deconstruction of one of my great days:) Today:)
Sight Seeing a stranger smile. Reading nice things people write and say. Cloudy sunset putting makeup over an ordinary city to make it beautiful.
Feeling Talking to like-minded people. Making new friends. Knowing I’m not alone. Not feeling so alien in a place where walking with a smile on your face is perceived as crazy. And they don’t even scratch the surface of how crazy I can be:)
Sound A friend on the phone telling me she misses me. (connected) The same thing happening to someone else. And of course, wonderful music. Hackett & Hackett playing Satie.
Movement 
A chain of small victories. Driving home after a long day. Back to a loved one. More Satie on the way. Breathing in the air, nicotine and life. Speeding. Living. Sipping coffee at home. Awake.
Being here.
Being now.
Being. You.