Faith, to a large extent, stems from opinion; if a person acts with reason, it forms as the emotional content of that person. "Where your treasure is, there your heart will be." This is exactly what is said in the Gospel. It's a wise statement, very insightful and observant.
I have seen many different believers in my life, both those who act with reason and those who act with their hearts... it's all very multifaceted. I have also seen militant atheists in my life during the Soviet era. They also acted based on their faith in the communist future of humanity (either through reason or through their hearts), and they considered religion to be a delusion, just as believers consider atheism to be a delusion. Everything is essentially the same in this world. The only difference is the objects of worship.