Have you ever noticed that parents, especially those with small children, can be incredibly touchy? Reprimand their kids, and they quickly get huffy because they think you're criticizing their parenting indirectly.
People are the same about investments. Bring up an investment that's gone badly, and 9 out of 10 investors quickly get very defensive. Same story - criticize the investment, and you're basically criticizing them.
It's a natural reaction. In an old post, I called it a symbolic interactionist approach to investments. Humans act toward things on the basis of the meanings they ascribe to those things. The meaning of such things is derived from the social interaction that one has with others and society. Our investment decisions are tied up with our self-worth as investors, and our wealth is joined at the hip to our perception of social status.
But it's the wrong reaction. Jerry Goodman, aka Adam Smith, wrote about this in The Money Game. "A stock is, for all practical purposes, a piece of paper that sits in a bank vault. Most likely you will never see it. It may or may not have an Intrinsic Value; what it is worth on any given day depends on the confluence of buyers and sellers that day. The most important thing to realize is simplistic: The stock doesn't know you own it. All those marvelous things, or those terrible things, that you feel about a stock, or a list of stocks, or an amount of money represented by a list of stocks, all of these things are unreciprocated by the stock or the group of stocks. You can be in love if you want to, but that piece of paper doesn't love you, and unreciprocated love can turn into masochism, narcissism, or, even worse, market losses and unreciprocated hate."
You are not your investments. Thinking otherwise puts us at risk of committing a mortal sin of investing, if we allow defensiveness to cloud our scrutiny of a prior decision.
And by the way, the same logic should apply when your investments are doing great. Congratulations on the victory - but you're still not your investments.