@thetruth36 you can make trades as per the USD chart into the BTC market. The point of the @haejin is that when bitcoin value is increasing but the coin $ value is not increasing then in chart you might see a downfall of the coin.
I cannot explain this whole concept of considering USD value while buying a coin. But if you notice in this current market then you will see a clear difference.
Just to sum up "Buy on BTC market but keep track of USD value of purchase"