A Fundamental Approach towards Taking Profit/Stopping Loss

As a long term fundamental investor, the question of how to set the profit target or stop loss point is based mainly on my investment thesis for each of my stock investment $Alibaba(BABA.US)$, $Apple(AAPL.US)$, $Bank of America(BAC.US)$, $Microsoft(MSFT.US)$, $NVIDIA(NVDA.US)$ in my long term portfolio. Once the company fundamental changes, this will be the trigger point to take profit or stop loss. In terms of financials, a company showing slowing revenue or profit growth for consecutive quarters hint that the fundamentals may have deteriorated which could affect the intrinsic value of the stock. Another area to monitor will be the company's market share. If the market share is slipping due to more innovative products or better services offered by competitiors at more competitve prices, future challenges may lie ahead to boost the company's sales or earnings. A change in management will be a significant issue of concern, particularly so when unwise decisions are made, like in the case of the new management taking up excessive debt or venturing into questionable businesses. In general, substantial changes that contradict my investment thesis will be the determining factor for long term investors like myself to offload a portion of my holdings. As for now, I have not observed any fundamental changes that will affect the underlying value of the stocks in my portfolio and will continue to hold the stocks so long as they run high quality businesses at reasonable valuations.
$Dow Jones Industrial Average(.DJI.US)$
$Nasdaq Composite Index(.IXIC.US)$
$S&P 500 Index(.SPX.US)$