There are days when things just fall together and you see growth. The improvement is obvious and you throw yourself a parade right there in your head over such an accomplishment. It's such a great feeling that you might could convince yourself it will always be so and never revert backwards. And then there are days when things just snowball down the hill into a complete failure no matter how hard you try to prevent it.
Marriage is like that. You work through problems and come out feeling fantastic. The relief of being on the same page is intoxicating enough that it is easy to forget there will be other disagreements. Maintenance is never done. For a long time, the concept of maintenance has been so disheartening to me. I hate having to do things that will always have to be done and there is no real completion point. Relationships are all that way, unless you are looking to end them. There is always some kind of continual investment that is required.
Even when you think you have maintained things properly, there can still be trouble and unforeseeable problems. When those arise, it is tempting to throw in the towel and forget the purpose of being in that relationship to begin with. The purpose should never be to have a perfect relationship where everyone always agrees and there are never any problems. The purpose of any relationship is to benefit each other through growth, learning and maturity - like those precious metals in a fire, being refined and purified. With people the process is never done.