Knackered from a full day's work!

Being self employed most of my working days are spent working from home or going out to schools or clients for various film, animation or web projects. However, I had a full day teaching film at Wiltshire college today and feel exhausted - the lessons went really well, but were very intensive, and I've got a feeling I must have a cold bug as I have very little energy!
Thought I'd take a photo of my ID badge and diary to remind me that other days are not normally this knackering!