I used to be a total eraser hog and take FOREVER to complete a drawing, even a quick sketch. I've gotten a lot better recently, and during my LoA sessions I intentionally "forget" to bring an eraser so I force myself to commit to whatever I do. In the quicker drawings it allows me to really easily see where I went wrong, and I find I am able to give myself better feedback.
I recently have been letting my eraser sneak back in for the longest drawings of the session, only to remove small detail mistakes, but I'm not sure if it's helping my technique or not yet.
Do you use an eraser in your practice sessions?