We often feel like our relationships aren't working. The only way to know for sure is to be clear on what your goal for the relationship is. If you're clear on the goal then it's simple to see if what you're doing with the relationship, what you're 'using it for', is bringing you closer to or pushing you further away from that purpose.
For example if your goal is to learn how to truly love another person then the times when you are feeling unloving, or choosing to see them as undeserving of love will be given the purpose of practicing loving them regardless of their behavior and then looking honestly at your resistance to doing just that. Their role in your life becomes then a part of the lesson of learning the meaning of unconditional love and your resistance to it, your fear of it. It's easy to feel like we love someone when they're being everything we think we want them to be. It's when they're NOT being what we think we want them to be but we choose to continue loving them anyway that we understand the meaning of love without conditions.
To my mind that is the proof of the relationship 'working' as the goal was conceived. And really what greater purpose can there possibly be for ANY relationship than learning the meaning of unconditional love? And if you don't have a conscious goal, then how are you supposed to know whether or not what you are doing is actually working?