Ok it seems more general than I thought.
Well I restarted a fresh save and still got more than the three promised lifestyles. I'm at 6 atm, and avoided the dreaded frequent traveler and its +5 bored, as well as junk-food afficionado, or whatever it's called, which are the two most punitive I've found
@Sharonia I think your sim will gradually forget the single and loving it, and lean towards hungry for love overtime. However, it seems like, as lifestyles are poorly coded, this might push your sim to autonomously cheat, since they will 'prefer romantic behaviour'.
Again, the only way I found to get rid of lifestyles is to let them die, simply.