I've never thought the wish to "meet someone new" had anything to do with a failing relationship (romantic or otherwise), as children roll it all the time, especially when they're newly aged up, have no friends to turn on yet, and haven't had much time to get mad at their families. I have however seen the wish to "meet a compatible sign" after a breakup, which I ignore unless I really want the points. But I do kind of wonder whether sims care about that kind of thing. It would explain some of the more baffling attraction scenarios. But I personally don't care about that possibility—there's no room for astrology in my life or in my game.
@Mikezumi I almost never see my sims roll a wish to break up, even if the relationship bar really starts to drop. I think the only time I even see a wish to be mean is with an inappropriate sim, and that's kind of the point. But maybe it's because I play on normal lifespan; I know yours is even shorter. If the breakup wishes are somewhat dependent on the absolute amount of time two sims have been together, it would make sense that you never see it while other players' sims roll the wish all the time. Perhaps it's the same for other family relationships as well. And even if the chance of rolling that wish stays constant, you still have far less time during a sim's life to see it than others do.
Regardless, my sims are not breaking up a long successful marriage just because one of them happened to hit on the ~1% chance of rolling a wish for divorce. I figure if I can get them to want to be together again with a couple of compliments, than it really wasn't more than an idle thought in the first place.