Ego..
Ego has only three letters but if it goes enter into a relationship anyhow then it is able to destroy the relation. I have seen in many cases it tries to enter where there is much happiness or love. Relation could be any such as husband-wife, friends, girlfriend-boyfriend etc. and only one word ego is enough to separate any relationship mentioned above.
How ego emerges & When?
Ego can not enter into any relationship until they have proper understanding but it can enter easily when any one start showing that he/she is more wisdom than other (May be husband or wife anyone) and in same situation if the second one starts feeling that she/he is wrong and i am right, it means both have ego. When ego capture both of them only ego win and relation became defeat.
It means relationship is weaker than ego, hence don't give chance to enter it into any relationship.
We can protect our relation if and only if we ready to compromise.
Thanks
@face2face