You've forgotten something, its fairly important so you start to sweat because now you have to make a decision. Do you stop, in the middle of the street and embarrass, (I don't mean you stand there and piss yourself just to take the focus off the fact that you have forgotten something or on the other hand it could be a handy diversion, your choice) yourself in front of all these people who will know as soon as you turn, say to themselves 'ha that twat has just forgotten something and he knows that we know, thats why he's sweating!'.
Or the second option. The one where you don't sweat or look like a twat. Its the cowards way out but in the first few moments of thoughts it seems to be the best option.
There is one other option which unlike the 2nd it takes a few more moments to realise and plan out, how, when and where you do it. Its more of the first idea but requires a bit of over acting. The move goes as so:
You firstly have to prepare yourself mentally. Commit to what it is you are about to do there is no backing out once you have started. Either go hard or go home. Secondly don't think just do it. Stop, turn around but in doing so dramatically flare your hands in the air and as loud as possible say 'I've only gone a bloody forgotten something!' finished off with a big tut and put your feet down a little louder. Its a little embarrassing but I suppose I depends on how important the thing you forgot was. The choice is yours.