Monday marks the 15th annual Positive People Day, a Boston tradition that encourages people to “commit to kindness.” The holiday began as an effort to curb violence by the organization Victory Over Violence. The group’s founders, W. Watts Biggers (co-creator of the “Underdog” cartoon) and Nancy Purbeck, suggest that taking a few minutes out of your day to do a small positive act — a hug, a smile, or a “thank you” — will help that effort by creating a less hostile atmosphere. Volunteers throughout the city pass out cards featuring pictures of Underdog and positive messages. Because this year’s Positive People Day falls near the end of a particularly divisive and contentious election season, we asked Purbeck, who splits her time between Boston and Manomet, about the negativity caused by politics.