When I was a poor student, I carried around a small notepad in my pocket and a pencil and wrote down every transaction. Only way I ensured discipline to not was

When I was a poor student, I carried around a small notepad in my pocket and a pencil and wrote down every transaction. Only way I ensured discipline to not waste money and then go hungry later. But now I am ruined by smartphones, which are way too slow to type in every transaction manually.