The best way to tell is the colours, you will notice it looking dull then the eyes start to cloud, even with snows. I can even spot it in my blizzards. The eyes will clear and the colour return slightly for a day or two then you will get your shed. The mood thing is quite normal during ecdysis(shedding), it's just uncomfortable for them, and i think they probably feel insecure due to their hindered eyesight. Hope that helps.
Sean