When you get sad after your sim dies. I've never really played Sims with aging on until this year, and I haven't experienced the pain of losing a sim.
Either I've been playing Sims for too long, or I'm just over-emotional LOL.
I usually get pretty sad when I'm playing a legacy and my founder dies. Like, I remember creating you. You got that job and climbed to the top. You found that special someone and marry him. You had your first son and taught him how to walk and talk then watch him as he grow up to be a man.
I could go on about that but mhm.. So. Many. Memories.
Like yeah they're just a bunch of pixels but to me Sims are like pets in a way, you basically take care of them (well I'm a control freak, I control everything) and you've spent a lot of time with them.
That's how I feel during my first weeks of playing legacy. Though I've gotten over it now xD