In reality: Faithfulness is the main core of a healthy marriage. Trust should be at its highest order.
Once you are in a relationship that is the commitment.
If you have children then you have responsibility.I believe that a relationship is between two people who care for each other,who can talk to each other about their problems. I believe a relationship is about going through good times and bad.A relationship shouldn't be all about making out. It should be based on care, responsibility, commitment, faithfulness, maturity, talking to one another, etc.
Faithfulness being capable of maintaining yourself, while you are around other attractive people; and to be true to yourself as well as your partner. Trust, takes alot of time and effort to build up, yet it can destroyed in an instant.
Being honest with each other and being able to speak the truth without fear is a crucial part of a true relationship.
You must be honest to your partner about things that you are feeling, thinking and doing. How honest can you be with your partner? Be as open as you can. Both partners need to accept responsibility. Each considering the various aspects before deciding and acting. Protecting each other from harm and not blaming each other when things don't go right. You must treat your partner like no one else in the world matters to you except them. Love does not flourish by it's self; you have to work hard for it. If there is a gloomy side you have to enhance it, then it will blossom. A good relationship is for better, for worse, for richer, or poorer, in sickness and in health.