This is so true, and something similar has been said by saints and philosophers. It was quite a surprise to me when I first encountered this idea, but the more I learn about love, the more I find that this is true.
Thank you so much for your insightful comment, Clare. It is so simple, but it is not always so easy, especially if the friend does something that hurts us: but a friend loves at all times, no matter what. May God bless you and your dear ones.