I start trading when the year 2017 and my capital that time is only 50$ worth of bitcoin very small amount but in only one month I double my capital. So I continue trade until my capital grow. I earn money for trading because in that year is very good to trade the bitcoin is so high and the other altcoins are very good to trade in short time. But now I stop it because bitcoin drop and almost altcoins are follow.
That's nice if you got double profit from trading in 2017 and at that time I am sure many people got such huge profit. I think getting double profit in such short term of trading is all about the worth of the coin and as you said now the price of altcoin has dropped down. Price matters a lot and if you trade in right time you will get exactly approximating doubled profit.
if we trade at the right time then profits can multiply, and in fact there will always be the right time to start trading but this requires the ability to find the price action time.
so prepare yourself before trading, because market conditions can change.