Fear and Greed are the big enemies to achieving strong and consistent returns in the stock market.
Fear may lead to premature selling and greed may lead to not selling soon enough. (among other things).
Discipline and established exit strategy (set in advance) are beneficial qualities.
I'm a former licensed securities portfolio specialist, but my personal strategy for myself now is to use professional fee based asset managers, to avoid commission conflicts, and set up portfolio strategies with ranges of expected returns based on risk, while I focus on my full time employment in another industry. (and family, and my GT)...
And then, since I still enjoythe financial markets, I keep a small portion that I "trade" with, meaning stocks that I may buy and sell in less than a year's time. Ideally, I try to keep them longer than 12 months, for tax purposes...But it doesn't always happen that way, since I'm not afraid to take a profit and pay short term capital gains taxes.
(Just my personal strategy, not intended as investment or stock advice)...