This ancient Finnish word describes an attitude of courage, resilience, grit, tenacity and perseverance. This key psychological competence enables extraordinary action in times of adversity. To have sisu confers a further dimension of doing so with honesty, integrity and humility. Sisu is a universal trait. It may have been bottled and labelled by the Finns, but it is within reach of everyone. It lies within you, and you are very likely to have used it already.