More often our relationships are superficial or adversarial. The superficial ones have minimal impact on our lives. It's the adversarial ones that challenge us the most, yet if we look for the gift in the relationship, the awakening it offers, we can make important decisions about our lives.
Most of these relationships are there because we need to face our "demons" or our erroneous thinking. Sometimes this requires staying and working through the feelings it evokes. Sometimes it means being courageous enough to walk away because staying would mean repeating a pattern we've allowed for so long. Is this considered running away? No. As long as we are mindful of why we are making our decision, it is simply choosing a better experience.
Sometimes the transition can be scary, even lonely, but be assured that trusting in your decision will carry you through to new experiences. Depending on the scope of your past experiences that the current relationship mirrors, your choice could even lead you to a whole new life!