When my relationship with P ended, I had a near breakdown. She was my first true loving female partner. She was the first woman I had fallen in love with and been able to explore that love with on a romantic level (my other female love was straight, other female partners I did not love). She was the first venture I had taken into an openly poly relationship. I have not yet shared the end of that relationship on this forum, but it nearly destroyed me. (Suffice it to say I don't agree AT ALL with the concept of "the third having the most to lose".) Without being able to lean on N, I don't know if I would have survived. I questioned everything from my belief in the validity of poly to my sexuality to whether I had a right to remain married to my husband and parent our child. But N was there. N loved me through the good and the bad and held me through the worst of it. After some time he ran out of things to say and do to comfort me, but he was still there repeating himself when I needed it. Without that support and compassion from him, I don't know if I would have been able to remain in a relationship with him, or ANY healthy relationship.
You should be able to lean on one love over heartache caused by the other, at least to a point. I know N's capacity for helping me heal has brought us closer and made me a more loving and compassionate wife to him and further fueled my trust in him and the strength of our love. He is my life love and my best friend. We are there for eachother to lean on, regardless of the reason one or the other needs it.
When your grieving is over, just be sure he knows he's appreciated. And be sure to be willing to always provide the same compassion for him, regardless of the reason it is needed.
I'd rather be hated for who I am than loved for who I am not.