Happiness/Unhappiness comes from within, it is not related to outside factors.
We all know people who have a seemingly good life, health, parnassa, kids, happy marriage etc.. and yet they are miserable. On the other hand we all know people who have many challenges in life, and yet they’re happy, they are mekabel yesurim be’ahava.
We create our own misery with our thinking – with the way we perceive our reality. Some people perceive the cup as half-empty, others perceive it as half-full.
Our thoughts create our reality.
Emunah is one of the tools with which we can influence our thought process. If we truly believe that everything is orchestrated from above, and whatever Hashem does is good, we won’t feel the urge to fight Hashem’s decrees. When we relinquish control, and allow Hashem to do his job, we gain inner peace, and that’s the key to happiness.
When we find menuchas hanefesh within, we don’t need to change anything on the outside.