It's all relative.  If you play the long game in the market you're going to have ups and downs.  So long as your portfolio is trending upward over a long enough time horizon, you're substantially beating inflation, your money is growing, etc. then you're doing fine. 

Its all about goals.  If you are retired and needing to live off your investments then you should be in mostly low risk, predictable rate or return investments.  A good chunk of your portfolio in t-bills, low risk REIT shares, and blue chip or safe tech stocks. 

If you're younger and looking to grow your money for future retirement you should be balancing risk with reward over a long enough time line.  This is when you can afford to play with riskier tech stocks, and take advantage of market volatility. 

Most advice is good, but it doesn't work in a vacuum.  An 8% drop is substantial, but an 8% drop from where?  If I purchased a stock two decades ago at $5/share and it's peak was $80/share, and it drops to $73.60/share and I sell it I'm paying cap gains on $68.60/share.  That may not be the best strategy, incurring significant tax liability in a year when returns are also going to be down. 

On the other hand, if I bought it at $80, and it drops to $73.60 as the market trends downward its prudent to get out.  You now have the option to take a $6.4/share loss on your taxes this year, or save that loss to offset a gain in another year.  You can also stockpile that money and buy back in at an even lower share price and still look to make your loss back, or even turn it into a gain. 

I ran my own portfolio for years and did quite well, but once the internet allowed everyone to trade for free the market went all kinds of wonky.  Now you either have to watch it like a hawk, or find a trusted financial planner to watch it for you.  There's arguably even more money to be made now that ever before, but that reward comes at substantially increased risk.  That risk can be mitigated, but it requires constant vigilance. 

And, the Prez is right, its coming back and it will be bigger than ever.  I'm thinking the Dow hits 30k on the rebound.