Married couples should always be mindful of a kind of anger that can poison and eventually kill their marital relationship, an American priest based in Washington D.C., said.

Father T.G. Morrow said based from his years of experience counselling and giving advice to Christian couples who have marital issues, he found one major reason why marriages fall apart: sinful anger.

"Anger is a poison," Morrow told the Catholic News Agency. "If a husband and a wife are angry with each other a lot, it destroys the relationship. It makes it so painful that people want to get out of that relationship."

Everyone experiences the feeling of anger, explained Morrow, a theologian who is also the author of the book called "Overcoming Sinful Anger." Sometimes, anger can be righteous, just as St. Thomas Aquinas maintained. However, he said anger starts being wrong when it turns into sinful anger, which drives people to seek revenge.

When sinful anger gets in-between two formerly loving married couple, their relationship begins falling apart, Morrow said.

"It's extremely important that people realise that (anger) can be a very serious thing, especially if they have major outbursts that really hurt other people," he said.

"This anger, when it's expressed badly, is a poison to every relationship," he added. "Married people need especially to be careful about this...to work on this and to overcome this."

Morrow suggests that people counter each negative act of anger with five positive ones. Although getting anger is natural and unavoidable, Morrow said people should first consider if the situation they are in is worth getting angry about.

"People get angry about little, trifling things," he said. "You have to say 'Is this worth getting angry about?' If not, then you have to let it go. Just forget it."

Oftentimes, it is best if people simply offer their anger up to God as a sacrifice for their sins. "Anger won't go away automatically in one try," he explained. "We have to keep giving it to God as a sacrifice."