Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

Should I sell when my stocks are growing?
I reread your question. You are not asking about the validity of selling a particular stock after a bit of an increase but a group of stocks. We don't know how many.  This is the S&P for the past 12 months. Trading at 1025-1200 or so means that 80-100 points is an 8% move. I count 4 such moves during this time.  The philosophy of "you can't go wrong taking a gain" is tough for me to grasp as it offers no advice on when to get (back) in. Studies by firms such as Dalbar (you can google for some of their public material) show data that supports the fact that average investors lag the market by a huge amount. 20 years ending 12/31/08 the S&P returned 8.35%, investor equity returns showed 1.87%. I can only conclude that this is a result of buying high and selling low, not staying the course.  The data also leads me to believe the best advice one can give to people we meet in these circumstances is to invest in index funds, keeping your expenses low as you can. I've said this since read Jack Bogle decades ago, and this advice would have yielded about 8.25% over the 20 years, beating the average investor by far, by guaranteeing lagging the average by 10 basis points or so.  A summary of the more extensive report citing the numbers I referenced is available for down load - QAIB 2015 - Quantitative Analysis of Investor Behavior. It's quite an eye-opener and a worthy read. (The original report was dated 2009, but the link broke, so I've updated to the latest report, 2015)