Halliday & Matthiessen (2014: 706):
The ‘indicative’ realisation of proposals has the effect of blurring the line between proposals directed to the addressee and propositions about how the world ought to be. For example, through the extension of you from ‘addressee’ to ‘generalised person, including the addressee’ (in contrast with generalised they), we get general rules, general advice, and the like:||| If you find [[ yourself coming back the next day || and erasing more of the so-called improvements [[ than you keep]] ]], || you’d better get the hell out of that book. |||
||| If you are writing about something [[ that you have not experienced]] , || then you must supply yourself with experience. |||
||| You cannot drink on the job. |||