Often investors face preconceptions regarding the decision making to invest on stock exchanges, keeping a position already engaged, or liquidation of held positions. Regardless of market trends or the positions he holds, an investor should mentain an objective attitude, even though his mind tells him otherwise. We think in this case, for example, the tendency of investors to consider mistakenly the general market trend, just because their positions employed by them are contrary. Moreover, investors should be aware of the fact that market developments is always on the correct direction, as Warren Buffett says, one of the greatest investors of the world, “MS Market is always right”. The credibility of this work depends on the ability of investors to understand that the market can evolve at some given point apparently extremely random and unexpected, and not being controlled by someone. Therefore, we propose through this article, the analysis of the most important subjective factors that can influence the decision of investing on the stock exchanges, the level of acceptance of losses by the brokers, psychological level of 10% efficiency, modesty, greed and self-discipline manifested at one time by the market participants, but also the emotions and feelings involved in the investment process.