If you know yourself, you will always understand others better. And if you can understand others, there will only be one thing left in your relationships, and that is harmony.
Here is a discourse for you on understanding relationships. Following is an excerpt from the opening lines of the discourse:
For most people, their life revolves around relationships but an overwhelming majority are not happy with the state of their relationships. This discourse covers the spiritual side as well as the practical side. What is a relationship? Is it a transaction of convenience? Of needs? Of desires? Or is it a bond? A bond of love. Does a relationship come about because there is a bond or because there is a need?
In other words, is it because of the bond that people share common needs and therefore a relationship, or is it because of the needs that they get into a relationship and form a bond? The notion in the west is somewhat different to what is in the east. You may want to read about the secret of a good relationship.