When dealing with Libra ex-partner it really better to have a small argument from time to time if you want to avoid a big quarrel once. Libras are able to play nice for quite a long hiding their true feelings, but one day they run out of patience and turn into a real monster. When it happens, they can remember all the bad things ever done to them.
The key to establishing a good relationship with your Libra ex is being direct all the time without being blunt. In this case, the Libran can feel that he or she can be honest and open with you and will address his or her concerns to you. If will help to release the excess tension and help your Libra ex calm down.