One of the reasons I am in favor of taking pictures or recording your yoga practice every once in a while is so you can look at your alignment, and have a way to look back months later at how far you've come. Sure, a mirror could work, but I think it can be distracting during the practice to keep glancing over (and dangerous! Don't ever turn your neck when you're in shoulder stand!).
Anyway, it can also be pretty humbling, which is a positive thing. I've been feeling pretty proud of my progress with forearm stands. I posted about my fear of forearm stands six months ago, when I couldn't hold them for more than a couple seconds. Now, I am able to stay up and play around with where I put my legs. I gave scorpion a try yesterday, and while in it, I felt like my feet were so close to my head. I mean, I was sure my feet were a mere inch or two away from my head. Photographic evidence suggests I need to work on it more, haha. So another benefit of taking photos during practice? You'll have evidence of your humble beginnings. :)