When in the middle of work you stop and jot down a tubing run for a build in the future(including angled fittings if needed).
When your girlfriend wants to buy a gallon of spring water at the grocery store and you make her buy distilled water just in case you redo your loops AGAIN.
When you pee UV because of that one drunk night refilling your pc with feser 1 UV.
When you decide whether to buy certain PC components based on if they have water blocks made for them.