Words are so very very powerful. Words create the reality for which they stand. If you say life is cruel, life IS cruel, and you will experience life as cruel, unfair, and painful, and you will put yourself into a victim stance in relationship to life. I would suggest, that just for "fun" you say, "I often don't understand life." Or, "When someone I love dies, I feel really really sad."
When we lose someone, in death or in any other circumstance, our bodies call us to grieve. One of the ways we grieve is to cry. And I allow myself to cry for as long as I need to cry. If you breathe when you cry, crying will bring relief. The problem is most of us hold our breath when we feel the first surge of tears, and then crying becomes an unnecessary war of the wills.
By crying, we honor the importance of our relationship. Tears will soothe the pain of the loss. Check out google "What are tears good for." There are some interesting articles about the chemical make up of tears.
I also believe that those who pass on are still with us. So talk to your friend. Ask him to send you a sign that he is still with you and I guarantee you, he will.
Whatever you do, do not take medication. BUT, get plenty of rest, eat well, and talk to your friends. Share your grief with them. Do not drink and take any mind altering anything. Let safe people hold you and comfort you.
It is also a good time to look at your own passing which is also a guarantee. Once we get over the fear of dying, we can live in a way that we have never lived before.