In the workplace, the key to happiness is not to have a job, it is to have a purpose.
Being successful is not necessarily what we need to focus on. Being significant is what matters. With your contributions in the workplace, success automatically happens, and you will be appreciated. Surround yourself with people who know how great you really are, and this fuels your energy to make a difference.
I consider myself to be a happy person. I love my job, but most of the time, it does not feel like a job. It feels like I am meant to be here, and make my contribution, and make a difference.