When I have a problem, i am very guilty of taking things into my own hands, I recently got a new rubber strap which I had a lot of difficulty fitting through the screw in bars on my watch. So much trouble that i have scratched the brushed lugs which annoys the hell out of me (eventhough,nobody else will notice). In addition to that I put the strap ends in hot water to soften it and get it on more easily, it appears that this has made it shrink a little and I am left with a tiny gap between the lug and the strap which again drives me crazy. So now its off to the watchmaker to get the lugs tidied up and the strap while useable will be probably coming off. The whole exercise will cost a bit and its all for nothing!!
Have you got any examples of mistakes which have put you out of pocket?