Let’s say you go into a dark house.
Your rational instincts lead you to search for a light switch on the wall to the right side of the doorway at just under shoulder height. It leads you to do that because that is where your experience indicates they usually are; your reason allows you to abstract a pattern from the universe and reimpose it.
Your faith lets you, or drives you to persevere even when you discover that the light switch is not in the “right place.” It allows you to, or, again, perhaps compels you to feel your way forward even when there is no information to solve your problem or when the information you have does not help.
Without faith, you would, upon discovery that the light switch was not located in the place it “should” be, sit right down and give in. Reason would say, “Light switches are located in such-and-such a place, therefor, if the light switch is not there, there is, perforce, no light to be had.” End of discussion.
Without reason, you would rush into the house and right down the stairs. You would lie there, with multiple breaks and contusions, content in your rock-hard belief that light will be “given” to you if you simply believe hard enough. And that’s how you’d die.
The constant dynamic tension between reason and faith, between nous and imagination, is the motive force in the human psyche. Or, you know, whatever.