That is not the case. It is rather he or she who never quits. Rather, it is about never ceasing to care. It's ok not to feel affectionate then. A mountain-climber can feel fatigued.
Life is an uphill struggle.
You've been demoralised before. The mountain of life stretches on endlessly. There is no hilltop from which you can scream victory. Your marriage is not a facet of your life. It is your life.