Respond to these rapid questions in our Sisu quiz and we will tell you which Sisu character you are. Play it now.Sisu, which is often demonstrated in circumstances where victory is improbable, is amazing tenacity in the face of great difficulty. It shows itself by acting against the odds and exhibiting bravery and tenacity in the face of difficulty; in other words, by choosing a course of action and then sticking with it even if it leads to repeated failures. It resembles serenity in certain ways, but sisu also involves dealing with stressful situations. The Finnish word sisus, which means “interior” and “entrails” or “guts,” is the source of the English word “gutsy,” which invokes a metaphor akin to this one (and found in other languages). A nearly related English term invokes the metaphor grit.