limit the words in the post content and add read more link

As you can see into the code, the routine is to display the post which has an id of 266. Now all I want is to limit the words displayed in the post content of that post. Let’s say, I want to limit the words to a number of 300 and then add a read more link.

This is the code I got so far:

    $post_id = 266;
    echo "<div id='widgets-wrapper3'><div id='marginwidgets' style="overflow: auto; max-width: 100%; margin: 0 auto; border: none !important;">";

    $queried_post = get_post($post_id); 
    echo "<div class="thewidgets">";
    echo $queried_post->post_content;
    echo '</div>';

    echo "</div></div>";    
?>

I always have the same problem with post excerpt, post content. There’re various hooks and functions for this purpose, like @kaiser pointed out. But sometimes they don’t do exactly what I want.

Here’s my solution, I write my own function that take the post content, and truncate it into specified number of words:

function wpse69204_excerpt( $num_words = 20, $ending = '...', $post_id = null )
{
    global $post;

    // Truncate post content
    $current_post = $post_id ? get_post( $post_id ) : $post;
    $excerpt = strip_shortcodes( $current_post->post_content );
    $excerpt = wp_trim_words( $excerpt, $num_words, $ending );

    // Read more link
    $excerpt .= '<a href="' . get_permalink( $post ) . '" title="">Continue reading...</a>';

    return $excerpt;
}