I'm sorry if I'm being captain obvious here, but if your sim is not a certain trait, eg. artistic, and the other sims is artistic, then the non-artistic talking about art to the artistic sim will take a long time to get tiresome for them and it'll boost your relationship even if you're enemies. Same for bookworm with books, family oriented and talking about family, workaholic and talking about work etc. Also, if you complain about, eg. art to an artistic sim, it'll lower your relationship.