We're all fully aware when we are unhappy, it tends to pervade everything else, but we only fully realise we were happy when it's gone and we're looking back at it from yet another unhappy state.
Let's try and realise when we're happy and - I dunno - celebrate it... or something. It certainly highlights for me the depth and insightfulness of that famous song,
"If you're happy and you know it clap your hands."
The dude who wrote that certainly knew what was going on!