If you only believe what you can see, then unless you can see the future, it doesnt exist?

God never did miraculous things for me when I was a believer. Serendipitous, happy coincidences occured just like they do for everyone. We were taught to attribute those to god, and report it in fabulist terms as a "miracle" or divine intervention; we were taught to attribute unpleasant outcomes to sin (or to Satan, but ultimately Satan can only function if we "give place" to him by sinning, so it still comes back to the fact that anything bad is All Your Fault somehow).

No wonder the Bible adjures believers to "pray without ceasing". If you really can approach that goal, then anytime something good happens there's a nonzero chance you would have recently requested that good thing, and you can credit it to god answering your prayer. If you don't get the good thing, or get bad things instead, then you must not have prayed enough, or with pure enough motives, or with enough faith, or without secret sin, or god is just saying "no" or "not right now" for Mysterious Reasons, or is chastising you or teaching you in some way, etc, etc.

And yes Christianity is basically the implementation / embrace of an interlocking set of logical fallacies that enable it. Religion in general relies on human propensity to confirmation bias and agency inference in particular, as well as all the other deceptions one can fall into if you don't actively work against them and have decent evidentiary standards.

this is how I think about the power of prayer.

I am a far more simple person than you. When told how god had helped someone through a tough time I simply ask "If god is responsible for extracating you from whatever, isn't it likely he played a role in getting you into the problem in the first place? Couldn't he just have prevented the misfortune from occurring? Why, do you suppose, it was necessary for you to suffer first?"