Create a Private Journal with BuddyForms http://docs.buddyforms.com/article/494-create-a-private-journal-in-wordpress

buddyforms_filter_cpt_listing_by_author.php

<?php
add_action( 'pre_get_posts', 'buddyforms_filter_cpt_listing_by_author' );
function buddyforms_filter_cpt_listing_by_author( $wp_query_obj ) {

	// First let us check if this is a page. We not want to restrict pages
	if( !isset( $wp_query_obj->query ) || isset( $wp_query_obj->query['page'] ) || 'page' == $wp_query_obj->query['post_type'] ){
		return $wp_query_obj;
	}

	// Check if the user is logged in and display a page to logged off users
	// Just change the page_id to the page you want to display 
	// If you want to only restrict a custom post type, move this block to line 23
	if( ! is_user_logged_in() ) {
		$wp_query_obj->set('post_type', 'page' );
		$wp_query_obj->set('page_id', '2' );
		return $wp_query_obj;
	}

	// If you want to have the Author Only Posts work only with a custom post type uncomment this 3 lines and change "custom post type" to your post type.
//	if( ! isset( $wp_query_obj->query['post_type'] ) && 'custom post type' != $wp_query_obj->query['post_type'] ){
//		return $wp_query_obj;
//	}
	
	// Let us get the logged in user
	$current_user = wp_get_current_user();

	// If the user is not administrator or can at lest delete posts show all posts
	if( !current_user_can( 'delete_plugins' ) ){
		return $wp_query_obj->set('author', $current_user->ID );
	}
}