public function delete(Model $model, $user = null)
    {
        if (! $this->isEnabled()) {
            return false;
        }

        $activity = $this->initActivity();

        // Auto determine user if none is supplied
        $user = $this->getUserId($user);

        $data = [
            'user_id'      => $user,
            'subject_id'   => $model->getKey(),
            'subject_type' => get_class($model)
        ];

        $activity->where($data)->delete();
    }