Sometimes, all of us have moments when our lives seem to go bad, we feel sad, we don't feel like doing anything... In these moments (and always), we need to think about the positive things have happened in our life.
I've read several books about "Happiness" and I've also ended a Coursera course called: "A Life of Happiness and Fulfillment". All of them agree that it is a good exercise to write 2-3 positive things that it have happened in our day. With that, we can raise our level of happiness.
You can also listen to this song called "The prayer". Here is the version with Celine Dion and Josh Groban.
I also recommend you to listen to this wonderful poem by Marcelo Posada called "Oración" (Prayer). It's in Spanish but it has subtitles in English. Enjoy and...be happy.