I *think* I have a possible solution, but I’ll leave this open in case you know of a better global way to nest these statements. I know just enough PHP is completely break a site. ๐
Possible solution:
<?php if ( is_single() ) {the_field('benefits');} ?>
<?php if ( is_single() ) {if( get_field('desire') == '90%' ): ?>
<?php echo do_shortcode("[PROGRESSBAR_WP id=3897]"); ?>
<?php endif;} ?>
<?php if ( is_single() ) {if ( function_exists( 'wpsabox_author_box' ) ) echo wpsabox_author_box();} ?>
<?php if ( is_single() ) {related_posts();} ?>
// To use on single post add "if (is_single() {functionality;}