Rewrite standard $errors messages output via function.php

Try this on function.php

    <?php
add_filter('login_errors', 'custom_login_error_messages');

function custom_login_error_messages($error) {
    if (strpos($error, 'Invalid email address') !== false) {
        return 'The email address you entered is not valid. Please try again.';
    } elseif (strpos($error, 'Lost your password?') !== false) {
        return 'Please click the "Forgot Password" link to reset your password.';
    }
        return 'Login failed. Please check your credentials and try again.';
}