Example is an indicator like Fibonacci retracement that indicates overbought market which indicates that you should sell, or that indicates an oversold market which indicates you should buy. Another is RSI that indicates a market you should enter but leave in short time like minutes after making few profits as it indicates the market may likely reverse back. Technical analysis is very important. This is the basic aspect new traders must learn about trading.
Looks like you have got something mixed up here, Fibonacci retracements help to determine the support and resistance levels and not over bought or over sold market conditions.
For overbought or oversold market conditions, you will have to use RSI or Stochastic Oscillator to help identify them,