Customize the added-to-cart and added-coupon messages

add_filter( 'wc_add_to_cart_message_html', function( $message, $products, $show_qty ) {

	$message = str_replace( 'has been added to your cart', 'is ready to check out', $message );
	return $message;

}, 10, 3 );

add_filter( 'woocommerce_coupon_message', function( $msg, $msg_code, $coupon ) {

	// Set message for specific coupon codes
	switch( strtoupper( $coupon->get_code() ) ) {
		case 'SPECIAL':
			return 'Lucky You! You\'ve got the SPECIAL coupon added to your cart!';
	}

	// Defaults:
	// 'Coupon code applied successfully.'
	// 'Coupon code removed successfully.'
	return $msg;

}, 10, 3 );