At some point when I was first getting into classical guitar, I got in the habit of not looking at either of my hands. I stare off into space or zone out — the equivalent of having my eyes closed. Looking at your hands while playing can be beneficial, but it has to be done right.
Look at where your hands are going next, not where they are. One of the biggest problems with shifting I see in my students is inaccuracy. Most times the problem is easily fixed: I tell them not to look at their left hand as it travels, but to look at it where its going.
The same principle can be applied any time you look at the left hand. Imagine what comes next, look at the frets and positions and strings you need to be at; imagine what the next thing to come sounds like and looks like. Don’t dwell on what your hands are doing at a given moment, always think ahead.
I find that thinking and looking ahead takes your accuracy to an entirely new, much better place.
Turn it into a practice method.
This can also be a practice technique. Play a piece or section only paying attention to one finger. What does it do? Is it accurate? If you have problem fingers (my left hand second finger tends to have the most issues), start by focusing on those.