There are a couple of distinctions. One is to avoid two extremes: a. rigidity and b. Chaos. If you or your partner have very rigid conditions, then it may be difficult to handle the unpredictable (p.s. the unpredictable is always predictable to happen) and the tough situations that will arise. On the other hand if there is chaos in your partnership (e.g. lack of boundaries and clear agreements), then you may be facing avoidable troubles (shame on you for not thinking it through). The third option is flexibility which may be more dynamic (i.e. moving and changing with the situation, growth and maturing of both parties and other unpredictable conditions) - this may require practices of honest communications, unfettered listening, bravery to face the truths (not just courage).. and the willingness to learn what to let go off and what to fight for in the relationship. These are abstractions I admit: lets talk if you want to regarding specifics. Kind regards