Art and Proportions
Most artists gather their own unique experiences as they go along and improve their skills. They discover neat little tricks and techniques on their own, often keeping these little discoveries to themselves. But since sharing is the big thing nowadays I thought I'd share a little discovery of my own rather than being oh-so secretive. It ain't nothing grand or fancy it's just a neat little trick you can add to your own bag of tricks. Let's move on with a simple analogy.
Acclimation And Proportion
We have all experienced travelling at fairly high speed by car (or by train or plane etc) and know how the feeling of moving fast slowly fades as time passes. The scientific term for what is happening is acclimation. When working on a painting or drawing over lengthy periods of time without any breaks, we experience something similar. Now, we can't change how our brains function but we can do a little mindbending and speed up our working process.
The Forgiving Eyes
When an artist works for many hours on a specific drawing or painting without taking any breaks his mind starts to dwell on things. He slowly builds up a tolerance for the piece he is working on, a kind of blindness for proportions, symmetrics, and shapes. His eyes get increasingly uncritical the more time passes. Most artists solve this by leaving the work for a while returning later with a less clouded view on their work. After a nice break flaws and errors will stand out more clearly. But how can we go about eliminating this tolerance without taking any breaks and thus become more productive by wasting less time on breaks?
A Simple Solution
The solution is actually deviously simple. All we have to do is to mirror our art work in any way we can and take a good hard look at it. Try working on a drawing or painting for some hours then mirror it and you'll see just how powerful this little trick is. With your art piece mirrored all flaws and errors will stand out disturbingly clear. So instead of taking hour long breaks wasting valuable time simply mirror your work, and almost instantly you will know what needs to be worked on.
Wait, there's more!
To end this tutorial I've made a short list of some ways to mirror your work. There are likely more ways to do it so just find one that works well for you.

Here they are:

  • Flip over your art piece and hold it up against a strong lightsource and look through it (works only with fairly thin paper)
  • Scan/photograph your art and open in your preferred graphics application and mirror it
  • Hold up your piece infront of a mirror

That's basically it. Thanks for reading and happy mirroring!