How cultivating gratitude is good for body and soul

The bible is unequivocal in calling followers of Christ to gratitude and thanksgiving. But what do psychological studies show about the impact of counting our blessings? Does an attitude of gratitude enhance well-being and mental health? Or might being over-grateful undermine self-confidence and cultivate a naïve ‘Pollyanna-ism’ that runs counter to common sense? How can we cultivate healthy, life-giving habits in our personal formation in Christ?