Associate Posts with individual user – hide from other members

The basis for making this work is actually pretty simple. Essentially, you just need to hook pre_get_posts and set the author query var to the value of the currently logged in user for each type of query you want to limit results on.

function logged_in_user_posts( $query ){
    if ( is_user_logged_in() ){
        global $current_user;
        get_currentuserinfo();
        $query->set( 'author', $current_user->ID );
    } else {
        // force query to return nothing if user not logged in
        // you may want to handle this more elegantly
        $query->set( 'author', -1 );
    }
}
add_action( 'pre_get_posts', 'logged_in_user_posts' );

Now, you’ll probably want to use some conditional tags here to limit what sorts of queries this acts on. For example, this will cause pages to 404 as-is, so you probably want to make sure the query is not for a page:

if( ! $query->is_page() )

EDIT- after a re-read of your question, I think perhaps I’ve misunderstood what you’re trying to do…