At the start of every turn, the user has a chance of recovering 20% of their HP based on their Luck(%) stat. It is learned by Mercenaries. While there are other skills that heal larger amounts (such as Better Odds) or heal more consistently (such as Renewal), Good Fortune is one of the earliest self-healing skills available. If a unit has high enough luck, Good Fortune can be a reliable choice of self-healing.
Heroes and Bow Knights can also learn this skill at any level, if they did not already have this skill. Bow Knights will only learn this skill if their base class is the Mercenary and not the Outlaw class.