Research has shown that about 50% of a person’s happiness is genetic, and about 10% is caused by our circumstances. And approximately 40% is under our control, due to our choices, frame of mind, expectations, lifestyle, attitudes, people with whom we associate, etc.

So, while many people feel like they’re a victim of forces not under their control, that’s at best a partial truth, for we can influence a great deal of how happy and contented we are, with a greater capacity for positiveness and wellbeing than we may realize.
https://neurosciencenews.com/happiness-genetics-19714/