How to show post which has the specific taxonomy terms?

Use this code instead.

$terms = wp_get_post_terms( $post->ID, array('competition', 'session') );
$term_slugs = wp_list_pluck( $terms, 'slug' );    
 $season = wp_get_post_terms( $post->ID, 'session' );
$season_slugs = wp_list_pluck( $terms, 'slug' ); 
$args = array(
        'post_type' => array( 'football_fixture' ), // profile and letter are CPTs
            'tax_query' => array(
                array(
                'taxonomy' => 'competition',
                'field' => 'slug',
                'terms' => $term_slugs
                ),
               array (
              'taxonomy' => 'session',
              'terms' => $season_slugs,
              'field' => 'slug')
            )   
    );


    $my_query = new WP_Query($args);