Our happiness does not have to be dependent on changing phenomena. Through the work of observing and training our mind, we can achieve the freedom of equanimity, considered one of the Ten Perfections in Buddhism.
Achieving equanimity/equipoise requires practice and right effort. We can use mindfulness as a tool.
The sublime quality of equanimity can become our default mental state through practice. With equanimity, we can be free of fleeting pleasures and achieve peace that supports us.