NVIDIA my second stock purchase on Degiro

In September 2016 I purchased 17 stocks of NVIDIA at $63.28 after months of listening to a good friend tell me about its driverless tech applications and how driverless cars will change the world, he had bought in at $20 a share in 2015. Then in October he said he sold all his NVIDIA stock saying “Goldman Sachs were getting involved which only meant trouble and the price was going to drop”. I wasn’t sure what to do as he was the one who brought the stock to my attention so I sold 9 stocks at $67.20 to reduce my exposure and kept the rest. The price then rose to $166 in July 2017 so I sold an additional 1 stock which left me with around $230 of my own money invested In NVIDIA for 7 stocks. The stocks are now worth $1,784 which is a great return and I’m not complaining, But if I had held on I would have $4,332 worth of NVIDIA now which would be a profit of $3,332. The lesson I learned from this was to not let myself be too easily swayed by other investors, do your own due diligence and if the stock is stacking up the same as it was when you bought it then keep holding it. Another cliche that comes to mind is cut your losers short and let your winners run....easier said than done but for now I’m still holding :)