First, Aristotle said that a true friend is 'another self'. The concern that you feel for your friend is the same concern that you feel for yourself, projected onto another person important enough to have become a part of you.
For that to happen, you must constantly leave open your heart and soul for the perusal of those important to you. That is the mark of true friendship. Certainly, those who know my weak sides and the dark, ugly parts of my soul are true friends to me, because I trust and love them as I do myself. Then it all boils down to this: it is not love, companionship, loyalty and all those nice ideals that define friendship. In the end, it is honesty.
Hard, brutal honesty to overcome the fear of judgement. Once that fear is overcome, you'll find that true friends do not judge because true friends understand that pure honesty is beyond judgement. True friends understand that this is who/what you are and it is strength on your part to have shown it to them.
Secondly, Grayling himself said that life is contract for loss. To live is to always be prepared for loss, because it is impossible for any life not to include any loss. (Unless one is to pass on before his loved ones, thus sparing him the agony of losing them.)
But life is always fraught with losses, and this is a condition I am still not able to come to terms with.
AH