For me, a lot depends upon MY mood. LOL. If I'm happy, I tend to be very nice to my sims and help them achieve their goals. I give in to their whims, let them find love, and keep them happy, too. On the other hand, if I'm having a bad day or am in a bad mood, my simmies had better look out! I might not be so kind on those days. I might have two sims who hate children try for a baby, or make one of those business managers spend time filling out reports instead of inviting a girlfriend over. I might even let a sim try fixing something when I know there's a good chance of electrocution.
The last time I felt really guilty was when I told my sim to light fireworks from her inventory. I really thought she'd be smart enough to take it outside first. Nope. She burned the whole kitchen down and died doing it. I did feel bad though, so I let her husband plead with the grim reaper. It worked. She's alive and well, but I doubt that I'll let another sim touch fireworks! Just kidding. We'll have fireworks, but I'll be sure they go outside to light them!