Perhaps it's carelessness and taking love for granted. Most couples don't make it because the first time they take each other for granted, they breakup and it's over. Successful couples work through that to find longer lasting happiness knowing that they've wronged each other in the past. That's okay to hurt each other, to see the hurt in each other, accept it, and learn from it. So, yes, dancing at the edge of love, you fall over once, you get up and then you try again.