How can I prevent a webform submission from being saved?

I'm writing a custom WebformHandler and am wondering how I can prevent a submission from being saved? I've tried using the RESULTS_IGNORED and SUBMISSION_OPTIONAL in the @WebformHandler annotation, but the submissions still get saved. Is there an additional step, say in the submitForm() method?

/**
 * Premium Content Webform Handler.
 *
 * This is a custom handler to tie into the premium content form to handle
 * when the user submits the form and either re-sends them the link to the
 * content, or takes them to the credit card processor to complete the
 * transaction.
 *
 * @WebformHandler(
 *   id = "lazy_handler",
 *   label = @Translation("Lazy Handler"),
 *   category = @Translation("Custom"),
 *   description = @Translation("Only saves on Mondays."),
 *   cardinality = \Drupal\webform\Plugin\WebformHandlerInterface::CARDINALITY_SINGLE,
 *   results = \Drupal\webform\Plugin\WebformHandlerInterface::RESULTS_IGNORED,
 *   submission = \Drupal\webform\Plugin\WebformHandlerInterface::SUBMISSION_OPTIONAL
 * )
 */
class LazyWebformHandler extends WebformHandlerBase {
  public function submitForm(array &$form, FormStateInterface $form_state, WebformSubmissionInterface $webform_submission) {
    $is_monday = FALSE;
    if (!$is_monday) {
      // Do I do something here to prevent the submission from being saved?
    }
  }
}