i was surprised to see the market today, everything fell in a short time, bitcoin fell around $1000 very fast and looking at coinmarketcap, all coins are red. a few days ago bitcoin rose slowly, but today was very surprising. What happen today? 
Don't be too surprised when you see a red market because we will see other surprises that can make us happy.After a decrease there will be an increase. So, don't overdo the response when the market is red.
The effect of decreasing coin prices on the market varies greatly, it could be due to a lot of FUD and other incidents.
In each dip, make good use of it to buy the coins you think need to be added then hold on until the market turns green. Of course, strong analysis is needed in choosing a coin, but Bitcoin doesn't really need a special strategy.
I recommend getting closer to Bitcoin by forgetting the obscure altcoins.