What gives you a "warm feeling" inside when playing?

A bunch of things:
some of the autonomous actions like parents hugging their kids or couples kissing each other's cheeks or the family sitting down to a meal together
when a build fits just right and sending a Sim into it proves that it works
sometimes just knowing that I didn't forget any of the usual suspects in a build (bins, sinks, fridges, etc)
puppies and kittens stumbling when they run
toddlers. all about them.
hitting a goal on an achievement
seeing a Sim slip in a puddle of mud
and a lot more small things that happen when I play.