Seeing an old couple walking hand in hand and smiling at each other.
The other day, I was at my favourite resturant at closing time when an older gentleman (80+) walked up the bar and ordered a coffee for himself and for his wife (of similar age): "A gin and tonic. But less tonic and less ice so she can have more gin!". After a while, they giggled themselfs out of the resturant, like drunk teenagers in love... ahh.. .to age like that. :)
And to continue the thread:
A sandwich with fresh bread covered in thick slices of good, aged cheese. And a strong coffee ...
Music. A solo string instrument up close, or in the headphones.
Just a slow walk outside on a sunny day.
Manual, repetive labour or handiwork. Yesterday I spent an hour sharpening my kitchen knives. Still feel relaxed.
An early morning before others are awake. Especially closer to summer, when the sun rises before most people.