I'm tired of relying on quick fixes to become a good artist.

Drawabox/Loomis/Proko and all that other shit aside, what can I do on a daily basis that will improve my drawing over the course of a few months, if even by a little bit?

Meaning: how long should my "drawing routine" be, what exercises should it contain, etc. Basically, how should my daily "art workout" be structured?