Tension and strife are part of any long or short term relationship, it is how you work through the issues that is important. The two couples love each other and were into committed relationships, but my friend found the tension between the couples very stressful, thus the comment.
I think the research shows that if a person is in a long term loving relationship they will be happier and live longer than those who are not in long term relationships.
My friend had also lost his long term partner and was just starting to come out of the grieving process and is I think, in the process of discovery of what he wants to do and what how he wants to live the rest of his life, so looking at others and his relationship issues is a starting point of discovery for my friend.
Life is short and we have to find our passion and continue to build and focus on our own hopes, desires, and dreams. Only by doing this will we be able to find happiness within and then reach out and allow loving relationships to grow because I still believe that love is all you need for inner peace and my hope is that my friend will come to this idea eventually.