It is not punishment inflicted on you by a grammar obsessed English teacher. It is not the last thing you do.
All writing is revision.
Revision is about reassessing what you have produced with new ideas, and making choices about what to do next. Revision may involve changing your thesis, re-structuring the essay, or adding or deleting evidence or examples. Revision most certainly should involve a thorough questioning of thesis, organization and support. What sounds good probably is. Note areas that sound like they need work.