Because you have a demon oppressing you. They are like a parasite sucking any positive energy from you and causing distress when the true path to happiness is mentioned, especially the name of Jesus. How do I know this? I have actually fought with these demons in the past, with a miraculous battle that was fought over me by the good and fallen angels. The good won, and my life although not a bowl of cherries, has been positive and relatively good since.

Oppression is the step just before possession, and it's almost as distressing. I bet you feel horrible most of the time don't you? You need to rebuke the evil spirit in the name of Jesus, command it to leave and use the actual name of Jesus as many times as it takes. However, I would suggest you call in a true born again Christian to do this, as it proly wont work if you as a non believer/hater of God/Jesus try it by yourself.