In the years I've been counseling and coaching, many people say, "I know I've been in sick relationships, but I don't know what a healthy relationship looks like."
There are many long and complicated answers to this, but there is also a simple one: healthy relationships make your life larger and happier; unhealthy relationships narrow your life and make you crazy.
Healthy relationships do not include mind games, mixed messages, or control. There is not a back and forth or continual makeup and breakup, or "I'm sorry, please forgive me" every week or so.
In healthy relationships, there is a partnership and a nurturing by both parties of that partnership. At the same time, each person recognizes the need to have interests and time away from their partner to nurture themselves. They don't need to have the same interests, but rather the same view of life. Healthy love is about taking care of yourself and taking care of your mate ... and those things are in balance to the point where they seldom collide.
Healthy people lead to healthy relationships and healthy relationships lead to real love. Real love does not seek another person to fill up what we are lacking. It takes a complete, whole person to really love and overly needy people cannot do it. Real love is balanced. Both partners love in fairly equal amounts. While the balance may shift back and forth, it is not lopsided. If you love someone who is not loving your back, or not loving you the way you love them, then it's not real.
When you place expectations on people to fill your empty places, that is not healthy. It's nice to have a partner, a companion, someone to help you weather life's storms, but it is not okay to look for someone to complete you or fix your broken places. That is not real love; that is dependence, codependence, and unhealthy neediness.