So, if you're lookin' for a real downer, check out Psalms 55. It's all about the pain and suffering of the speaker, who laments his enemies, who are described as "ravenous birds" and "vile men." He pleads to God for help, but also questions God's absence, saying that God has "forgotten" him. He also pleads for revenge on his enemies, and for salvation from his troubles. Yeah, it's pretty depressing. But hey, it's the Bible.