We think that giving thanks is just 'Thank you.' When really, giving thanks, giving something, requires something of us.
A man in sin always wants to hide. Fear comes from your sin, sin cultivates your fear. Because we sin, we cultivate a life of fear, so we don't trust, so we don't have faith. Paralyzed by fear we stay still, we don't move. We become immobile, apathetic.
The act of giving is the physical act of our faith.