Here's a helpful rule for those who might need it, and those who probably think they don't: Don't shit in your own kennel.
Simple rule really, one which over the years has worked very well. Here's three practical uses for the Rule:
Don't do your flatmates.
Don't do your partner's friends.
Don't do your friend's partners.
Life is a whole lot easier if you keep that in mind. Break them if you must, but do it knowing there will be consequences -- prepare for someone to be hurt, possibly you, but certainly someone close to you. Here endeth the advice.