Things I will never understand

I don't understand why people are struggling to survive while others have so much. I don't understand why the wonderful person dies way to young, while the creeps roam free. I don't understand why hearts have to be broken and depression can hit so hard you can't breath and I don't understand why I can't just be me, I don't understand why I am so broken, both physically and emotionally.
I have always been taught that I am to just have faith and that I am not to have to understand why. I don't understand I don't get why sometimes I feel like I just need to crawl in a hole or run away.
Today is a day I don't understand. A year ago I was so full of hope, hope that I would soon be better that my shoulder would not hurt anymore and that I would be able to have use of my arm. Now I am here another year has gone by and I am at a crossroads and I feel like I have circled the block and am back to the same place. No steps forward . Today I was told that my shoulder replacement is not working as hoped and I will have to have it converted to a Total shoulder replacement. I am so sad and feel like a failure I know that this is rambling but I just don't understand