t's late and we're a bit tired
I think thats a pretty reasonable one actually - maybe the bloke says it because he is really feeling like ****e after a long day - multi sectors - and is really saying keep your guard up.
I know after a long day with a few early starts in a row - I feel like crap. I know the reaction times drop and you can be focused on one thing and completely miss something else.
I think most of the other TEM is pretty much rubbish.