Believers have a great advantage over agnostics, they believe in metaphysics and as we all know, it is the belief that moves mountains. But agnostics have an advantage too, they are not biased by thousands of years of accumulated spiritual knowledge of what is supposedly right for you.
To use a Freudian expression, the believers have a spiritual super-ego burnt into their brains which is pretty hard to overcome if you ever have to. God, in Neale Walsch's Conversations with God, often used the expression useful rather than right. If you need to travel to a certain destination and you go in the opposite direction, He said, well, that's not useful.
Perhaps we can use the notion of running into a maize along our spiritual path. You know that the exit lies in the north, but you have to move south in order to get there. The point is that you have to become psychologically whole before you can become holy, and God and life only know what this entails for your personal journey.