Do I lose changes when I upgrade Laravel

In extension to this question : Laravel - login only with password

I am trying to modify in app\Http\Controllers\Auth\LoginController.php and RegisterController.php and in resources\views\auth the login.blade.php and register.blade.php

If I do modify those files, in the future in case I upgrade laravel will those changes be kept or I will lose them? Keeping in mind the question from the other topic, am I on the right path in modifying this files or should I do it differently?

via Chebli Mohamed