My head hurts. I've bashed my temples repeatedly on those god damn corners of the bonnet numerous times
Back of my neck hurts. That damn bloody boot lid never stays up so if you're scrambling about it the boot the lid keeps coming down on your head and the boot catch hits you in the neck
My back hurts. Leaning down into the engine bay for any length of time kills my back. Are full time mechanics basically as flexible as gymnasts ?
When you drop a nut/washer/bolt. You really do lose it don't you ?! - no space anywhere
All pales into insignificance I guess when you get out for a blast
- but I have been aching these last few days 
- I've taken to wearing a beanie even at the height of Summer to work under the bonnet.