Transition has taught me that the highest expression of love is unconditional. When someone loves you unconditionally then they love you for who you are on the inside, not on the outside, not for how you make them feel, or what you can provide or do for them. Unconditional love is rare, but it's the greatest love there is.
Though I'm not Christian, I always thought this passage from the Christian Bible in I Corinthians 13 was a beautiful description of unconditional love:
Love is patient, love is kind and is not jealous; love does not brag and is not arrogant,
does not act unbecomingly; it does not seek its own, is not provoked, does not take into account a wrong suffered,
does not rejoice in unrighteousness, but rejoices with the truth;
bears all things, believes all things, hopes all things, endures all things. Love never fails.