Three basic rules for love in a relationship.

First, love is pure. It needs to be unadulterated, unmixed, free of any other emotion. This part of love is very difficult to find. There can be no jealously. It is a feeling that will bring you a sense of joy and calm when you are with you partner. it is the feeling you get when you are together in the same room and do not need to speak. Just to be in the presence of your partner give you that sense of joy and calm when your love is pure.

Second, love is true. Your love needs to be real. It's cliché, but love must be from the spirit and heart. It cannot be guided and swayed by physical or material attributes. True love seeks the inner spirit, the soul of the person.

Finally, love must be unconditional. You just love. Not matter what. This seems to be the most difficult of the three.
A little test of unconditional love: lock your dog and your girlfriend into the trunk or boot of a car for an hour. Then when you open the trunk, which one will be happy to see you? That is unconditional love. (this is also a joke, don't try this at home.)
Even when we do something bad or when we hurt our partners feelings, if love is unconditional, pure love and true love will shine through and create a desire of forgiveness.
This is Unconditional Love

The best relationships will contain all three. I feel very blessed that I found that in my fiancé.