Nowadays people often have several romantic relationships throughout their lives. We date, we have boyfriends and girlfriends, and sometimes even multiple marriages. This means that relationships — the vast majority of relationships, in fact — end.
People refer to any relationship that ended as a "failed" relationship. For example, you might hear somebody say "he had three failed marriages before ..."
To talk about romantic relationships in general, many people have had wonderful, fulfiling relationships that were very rewarding, where the partners respected each other, helped each other out, shared some experiences, and learned about themselves.
Sometimes, because somebody had to move, or they grew apart, or someone changed, the relationship had to end. But this does not mean that the whole relationship was a failure. To look at all ended relationships as failures disrespects the joy and growth that many ended relationships bring people, and can give someone a negative and depressing outlook on their love life.
Its ended not failed