Find a short scripture verse, or a short prayer, which can be repeated with each breath. Focus on your breathing, and continually repeat your prayer. When I was close to death from adrenal insufficiency in 1985, I prayed this prayer over and over again, and I was able to focus on my faith rather than my fear. Believe that God can heal even the pain of grief. Believe that you will see them again, in eternal life.
Life is hard.
Fear is real. We have a choice about how to respond. We can let our fear paralyze us, or we can let it motivate us to do everything we can to keep hope alive. I know that God's love casts out all fear. I am absolutely convinced, to paraphrase Paul, that nothing in this life, not even AIDS, death, or grief, not even fear, can separate us from the love of God in Christ Jesus.