Take a little time and regroup before regrading assessments. Effective teachers know that making rash or "on the spot" decisions about feedback can negatively impact the learning process and the data. Encourage students to advocate and ask questions, but don't be quick to add add points, curve grades, or throw out questions. Always ask "why" students performed the way they did and lean on statistics over time to give you better insight. Students in each class and each academic year perform differently. If there's a learning issue, reteach. Don't simply bandage the issue and regrade.