Say you have an item that cost you a $100 last year but you’ve never used it and probably never will. Then you sell it on eBay and get $50. So have you earned $50 or lost $50?

I say you’ve earned $50 . Your original $100 disappeared ages ago.

Now that may appear obvious but investors often find it impossible to sell loss-making shares they wait vainly for them to come back up. Similarly some people would rather let their car rust in their drive rather than cut their losses.