When it comes to lying in a relationship, some falsehoods seem to be more acceptable than others. For instance, lying about who you hang out with every Friday night is obviously not OK. Lying about liking your partner’s taste in music, especially during the early days, can be considered harmless. But relationship experts say, even if your partner doesn't lie about big things, the smallest lies or lying by omission can still affect your relationship in a major way. If your partner can't be honest about a few key issues, your relationship may be in trouble.