I woke thinking about a story I read yesterday--the one about the ten lepers who were cleansed on their way to show themselves to the priest. Only one came back to thank Jesus (and he fell on his face at Jesus' feet besides!), at which Jesus responded--'where are the nine? Was no one found but this foreigner who returned to give glory to God?' and the man was commended for his faith and told that his faith had made him well--literally had 'saved' him!
It seems to me there is a significant relationship between gratitude and faith. One gives evidence that the other is there. And from my experience, even a speck of gratitude has the potential to increase my faith. For example...when I begin to feel stressed or anxious about something, if I will straightway begin to thank God for the situation and His knowledge of it, and His ability to direct my steps with regard to it... I can sense my faith begin to grow right then and there from that little seed of gratitude. For me, breathing out 'thank-you Lord' audibly (quietly) and continuing to thank Him makes me begin to focus on His ability for the situation rather than my confusion or distress. And then I begin to trust Him to direct me, to provide solutions. And He begins to make a way where moments before there seemed to be no way. I guess that's part of the reason we are instructed to present to Him our requests with thanksgiving whenever we are tempted to be anxious. It works. It changes my attitude from doubt to faith. Try it. It works. Just say, 'thank-you'.