Isn't it wonderful when your spouse or friend walks into the listening room and asks what happened?
"The system sounds so much more real, lifelike. What did you do?"
And your smile is huge when you know you'd just spent the afternoon repositioning the speakers, or added a new DAC.
Validation is especially gratifying when it's a new piece of kit. Why? Because I think inwardly we're all worried about fooling ourselves. Did we really hear that big of a difference?
And then, someone walks in unnanounced and nails it perfectly (without even knowing anything changed).
That certainly cements it for me.