How much time are you willing to spend monitoring your portfolio? This is a critical question. An individual's investment plan should be based on his level of interest in ensuring personal financial success. The more diversified a portfolio is, and the more complex your strategy, the more time you will need. To be successful, an investor mush map out a strategy that carefully matches his own personality and level of commitment.
Discipline.
Although many investors start with an approach that will work for them, the ability to maintain discipline eludes far too many people. This is caused by a variety of psychological issues, led by fear and greed, that tend to dominate predetermined financial strategies. During various stages of a stock market, different investment styles will work better than others. Sometimes a value approach will be in favor. Other times a growth or momentum style to accommodate the market.