Loss aversion is a really disproportionate anxiety about stuff that doesn't matter very much. So for instance, if you lose $5, you feel really bad about the $5 you've lost. You're cursing yourself. You're going through it again and again. If, on the other hand, you find $5, you go - hey, great, five bucks. And you've forgotten about it really quickly.
Tim HarfordIf the whole process of learning from failure means discarding stuff that's not working, but in fact, our natural reaction is to keep going, to throw more money behind it, to throw more emotional energy behind it... that's a real problem.
Tim Harford