Eric & Meg got into a big fight over something small when Eric questioned whether he and Meg were compatible. They were having conflict with each other for well over a decade and had difficulty resolving the conflicts on their own.
Half of married couples are together based on similarities, and the other half are together based on differences. Typically when couples commit to each other, each partner has already passed the preliminary screening process. Dating typically rules out incompatible partners.
Eric occasionally believed that when he and Meg fought, they were incompatible. However, the thought of being incompatible created instability in their relationship. Since marriage counseling was resolving most of their differences, the premise of incompatibility was unlikely. If fact, the better they got along, the more they expressed attraction and gratitude for one another. They appear to be compatible after all.