While typing this I ended up going on a bit of a tangent and inserting whatever came into mind, so it might not be entirely coherent.
Sorry. I'm posting it since I took the time to type it. The answer is no in the sense you can't just think and rewire your brain, of course, and often memory can betray opposition, but yes in that intellectual positions aren't exactly meaningful in the context of how one lives and thus, so in another sense, you can genuinely exist as a believer just as the believer exists as you do.
As humans, with our signs, language, culture, we spend much of our days thinking in ideas that we cannot fully know yet are either something you belong to (humanity, earthling, race, gender, etc.) or is a vague word describing a physical process or dynamic that swells or is confined based on absorbing other vague definitions (goodness, love, governance, etc.), all to a point where we overextend ourselves constantly and don't entirely mean what we say even unknowingly. This probably explains a lot of the problems with discussions of politics with democracy and parties. Participants in arguments/debates almost never compromise or give in. Existential crises that people often face as they grow older. And all the time I see people argue diametrically opposed to one another when from the outside it looks like they mean the same thing but the disagreement is coming from how it is expressed. Believing in gods and how such views still remain today probably shares the same kind of cause.
Is there really that much of a distinction between one's willingness to earnestly say in conversation that they believe an entity was involved in any of this and not? Is it impossible for an atheist to simply insert themselves into the unity of a religious communion without your mind repelling you out the door, or on the flipside, walk out not converted despite genuinely partaking in the mythology, traditions, and feelings? Does an atheist betray himself if, in a war, he charges forward with a feeling of permanence in the face of death, or is this dissociation with death just from our inability to comprehend it and existence is all we've known? If an atheist suffers great anguish and pleads to no one in particular, do we accuse him of faking his stance? What about when he goes to a grave and starts talking to the deceased, has he revealed himself to be a phony even if when he walks away believes the dead did not hear him even though the conversation was still just as mindful as he would've been if he felt otherwise? Maybe if you were religious you would try to spin these angles, but aren't these just expressions of emotion?
When a Smash Bros. player sits down at Grand Finals in a tournament and tells himself genuinely that he will win, do we accuse him of being a believer of some sort of mysticism and also call him a liar if he acknowledges after he loses that he did not literally mean it? Believing in others and ourselves is much like choosing to believe in something we "don't" believe in. Does a Christian betray himself if he doesn't refer to his Bible for all of his decision making in life every day? As atheists we could say he does because he reveals that he is really getting his conduct from "himself" and not the word of God, but we can't say he is a liar about his position. Is it irrational that our ancestors would hear a rustling in the bush and probably made the assumption that there was a predator rather than the more likely option of it being wind even if it was inevitably going to be more often than not the latter, thus through a sense of paranoiac anticipation we were saved as a species whereas other animals that could've been more right than wrong may have died off from their complacency? People can be hypocrites, cognitive dissonant, ignorant, presumptuous and I'm sure this applies to us all to some degree because of the nature of perceptions.
All of this might not make any sense, and it could all be me projecting because "coincidentally" I do not think my opinions are very definitive of who I am and I see instances in others where despite the power of the claims of positions others hold, it isn't entirely telling of them either. For example, most people here in America believe in a God, almost entirely the Abrahamic kind, but even within their own "sects" you couldn't as a result paint a picture of someone simply based on that description even if they say it's the most important thing in their life and regardless of how large the consequences of those beliefs being true would be. Imagine all the different people you've met in life, and remind yourself that nearly all of them "unite" themselves under very large labels that are supposed to define and thus confine them. Language is useful and we should be thankful it exists because it opens up our potential, but it'd be wise for us to exercise awareness of its abstractness because really my point is that it oft deceptively creates division just as it can create the opposite illusion, giving shape to things a bit beyond our scope. Our actions and the planet, universe, existence that we all share is for all intents and purposes truth, nothing more and nothing less. Even if we have every reason to believe things about reality, as far as our consciousness is concerned, it all ends with itself, and really consciousness, as an effect, and our subconsciousness that won't
truly know mortality until it goes away, in consequence has nothing to say about even that.