One thing I try to do frequently when painting (and don’t do quite frequently enough) is to step back about ten feet and look at it. It’s a good idea to do that at least every few minutes. By stepping back, you pull yourself away from focusing on the passage you’re working on right now and look at how all the parts relate to the whole. You see mistakes in proportion, symmetry, form, composition, color, and value. You see, literally, the big picture. And you work the kinks out of your back.
If you can’t remember to do this, then force it. Keep your palette 10 feet behind you so you have to step away. Keep the painting next to the thing you are painting, so you have to step back to a station point to see the view that you are painting. Or set a kitchen timer to go off every five minutes. Whatever you need to do to make yourself step away often is a worthwhile exercise.