“Everything is energy and that’s all there is to it. Match the frequency of the reality you want and you cannot help but get that reality. It can be no other way. This is not philosophy. This is physics.” — Albert Einstein
It is by the law of attraction that whatever thought you choose to focus on will be the reality you create. The reason is that every thought has its own vibration, and that vibration attracts whatever it is with the same vibration.
In other words, you’ve got to find a way to think of happy thoughts even in the midst of absence of happiness. And in time what you want will become reality.