Dumbstruck, a lot of people do what you are describing, which amounts to trading a lot based on gut feelings and various recipes like "sell if the market goes down two days in a row" (just an example).
Numerous studies of, say, clients of brokerages and their trades, reveals that this approach does not generate any extra returns, but it does generate extra trading costs.
What this strategy amounts to is being in and out of the market at essentially random times, and paying for it. The statistical outcome of it (without looking at trading costs) is not very different from simply allocating a part of money to cash and not trading.
Therefore, you would expect your returns (without considering costs) to be somewhat above the market if it goes down for a while, and below the market if it goes up for a while. Costs make you even less likely to win.
This approach is also very time consuming and that time could be used for better pursuits, for example reading financial literature or even fishing.
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