$current_author = get_query_var('author');
$author_posts= get_posts( 'author='.$user->id.'&posts_per_page=-1' );
if($author_posts){
echo "Mijn dagboek berichten";
echo '';
foreach ($author_posts as $author_post) {
echo '- '.$author_post->post_title.'
';
}
echo '
';
}
?>
https://wordpress.org/support/topic/list-of-all-posts-by-author