The way I am thinking about individual stock picking is as follows. Assume I do the analysis and decide that a certain stock is a good buy. I then step back and ask myself: am I right? And by "right" I assume "on average", not "certainly". To answer this question, it is not enough just to go over all the arguments again (or even look for a new data). You need to ask yourself a question: am I right based on what I do not know? To answer this question, I use the following simple logic:
1) I am not a professional and have limited resources to investigate the stock
2) There are many investment firms that have much more manpower and resources than I have
Now, it is more likely for them to be right than for me. If big players though that the stock was good, they would have bought it already and the price would have went up. The fact that it does not happen means that they do not think it is a good buy at current price. Since I believe them more than myself (as any rational person should), most likely, the result of my analysis is wrong.
Alternatively, you can think about this in a "winner's curse" scenario. Assume many people investigate the value of a stock. Assume the the value is $100. There is a volatility on value investigation: some may think it is $80, some may think it is $120. Now, assume the stock price is $100 but your investigation resulted in an estimated value of $120. What is more likely: the stock is undervalued or you are just among the people on the upper spectrum of the distribution?
And a special note for Phil-the-financial-exhibitionist: unlike yourself, I do not expose my financials to the world. Like I said, my stock pick and investment strategy s simple: buy low-fee market ETF like VCN.TO. Buy it when you have extra money, sell it when you need extra money. To save on trading costs, never buy or sell less than $15K worth. How much I make so far - I have no idea. I do not track my gains and losses as my current portfolio include buys at different times at different prices. But percentage return can easily be found by searching for the price online (just add the dividend yield).
And, for the Butler again (I am surprised how you went through school if you cannot understand a simple thing as I told you many times already): whether you make right or wrong decision is determined at the time you make the decision based on the information available at that time. The result of your decision (how much you actually won or lost) is just one realisation of the random variable that you have chosen by your past decision: it tells nothing about your expected return or its risk and it is mostly influenced by luck. It is like in poker when you call an all-in with only a gutshot draw and the turn gave you a straight: yes, you won a lot of money in that hand, but you made the wrong decision when you called.