Study a bit of skepticism, and then study some pragmatism. It is definitely a decision... it's just one we are not always consciously aware of. There is a lot of base assumptions we make, and based on those base assumptions, we often end up choosing an answer out of these hard questions. But yeah, it's definitely a choice, at some level of it
I grew up a New Ager/Spiritualist, and as I grew older I realized it wasn't working as everyone said it should be. Then one day I just looked at all the things my friends believed in, and thought about all the contradictions. Then it just occurred to me that if the New Age stuff worked then everyone would be doing it.
Seems logical if you believe in a Supernatural being, then you should be able to do supernatural stuff. No one can. So religion is just an Advance Fee Fraud, you pay up front in life, and you get the payoff after you die. Except, your dead.
Beliefs or lack thereof are not a choice. Being open minded, on the other hand, is a choice. You can force yourself to learn about different things from the perspective of people who believe those things, to understand the logic as they see it, and that may result in a change of beliefs - or not. It really just depends on whether the combination of everything you already believe plus the new idea is the most plausible of all concepts you've been introduced to.
Beliefs are not formed by choice IMO. I cannot choose to believe unicorns exist for example. Beliefs are a conclusion that best fits with the evidence as you see it. From that point, Atheism is the logical conclusion of the evidence as I see it. I didn't suddenly decide to become Atheist, it just happened.