When I think about slowing down, there's a couple things that I specifically do.
I pause before I make a stroke to make a "ghost stroke" then I make the stroke. If it doesn't look good, I undo it and try again. It ends up being a kind of zen/mindfulness practice.
For complex pieces, I leave them on my monitor for days so I can critique my own work. I do this at different stages on the process. Seeing the image separate from when I'm being creative helps me analyze why something looks weird. Sometimes, its obvious and I make corrections while drawing, other times I don't see the exact problem until I've stared at what I thought was (what I hoped would be) the final version for a couple hours.
How much time I have for a session will determine if I have to work on a piece for 10minutes one day and 45 minutes another day, but that time in between is just as valuable, because it gives me time to rip it to pieces to find out what I did wrong and what I did right.
In the end, you are the one who decides whether you are done with an image or not. And sometimes that's a difficult thing to do. Are you satisfied with the grid studies?
On your second grid study, on her hair, you have used a lot of lines, but you only really needed one "s" curve for that.
Another practice that is helpful is to take the time to refine the drawing on a new layer and work on generating a cleaner image. After a while, I stopped making so many searching lines and save time with the clean up.
