Custom loop inside single.php problem

I have add this custom loop before comment template in single.php page

<?php $my_query = new WP_Query('category_name=example' );
  while ($my_query->have_posts()) : $my_query->the_post();
  $do_not_duplicate = $post->ID; ?>
    <a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a>
  <?php endwhile; ?>

but now the comment loop doesn’t work 🙁
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