I-81 near Strasburg Va
Pascal's Wager goes something like this: If you believe in God and he turns out not to exist, no harm done; If you believe in god and he does exist then you will live eternally in Heaven; but, if you don't believe in god and it turns out that he does exist, then you will burn eternally in hell. In other words, it is better to believe, just to play safe.
As noble and admirable as that sounds - to just will yourself to believe the ridiculous, just to be safe - it is hard to imagine that an omniscient god would be fooled by such a ruse.
It is, of course a ridiculous notion. It is a specious argument with the built-in implication that there is no harm in believing something that is false. It also presupposes that one can override one's convictions and ignore the evidence which has fallen on one's eyes and will one's self to believe what one knows to be absurd.
This notion is not only false, it is dangerous. In the cases where it is not harmful, it is merely a condition of the reality that, even in a Darwinian universe, stupidity is not always fatal.
If one believes in something that is false, one has the potential to respond inappropriately or irrationally in a given situation. In the case of religion, these beliefs get quite adamant and have, historically, been backed up by violence, murder, and extreme forms of coercion.
So there is not merely the possibility of harm, there is a track record.