A good relationship will be characterized by LIFE - love, intimacy, friendship and empathy - all natural and genuine. Then there is no compelling need to complete it with a marriage for whatever reasons, for it will only spoil it. A marriage, on the other hand, is by definition, practice and experience more defined and compelled by law, custom, tradition - everything artificial fuelled by need for guarantees and security. The essential qualities of a good marital relationship is defined more by "woulds and shoulds" and by tonnes of counseling and guidance books! A chance of it turning into a good relationship (LIFE) is more of a lottery. An ideal natural relationship has 'life' while an artificially concocted relationship (marital) is more likely to die sooner than later.