When I was self employed I kept all my receipts including personal items. When I looked back over then I was shocked.
LOL I bought another piece of kit from my local running shop (UL 3/4 TAR mat as they had a 20% off day and it was cheap to begin with) and he checked if I was on their database as you often get 10% off if you go on their mailing list database. Anyway he let slip that it tells you how much you have spent in the last year. I foolishly asked him and it was £310 (exluding the £80 or £90 I was just spending). The worrying thing is that was one of a few shops I have bought gear from in the last year and was by no means the place I spend the most neither. In fact I'd say there was probably about 6 shops that I spent more at. Now that totally shocked me as I had always thought that the maximum amount of money I spend on gear to be outdoors with is £200 a year, AT MOST!! Hmmm! I wish I'd still got that dillusion, its not always good to know what you spend over a period of time. Much better to be self-deluding like I was but can no longer be with the facts I now know!!
PS There are no bad purchases just purchases which you could have done better. Learn from your mistakes and remember for every bad purchase you make. you will have the opportunity to buy something new to replace it! New gear is always good, right!!