The problem is not about trading altcoins or investing in it, but the ability to recognize opportunity and utilize that opportunity. The op already admitted that he made a lot of money perhaps from whatever he invested on (btc or alts) however he could not make the right decision as at when needed. 
One important factor in crypto investment especially altcoins is knowing when to sell during the bull period, the moment you fail to recognize that period and act on it the end result is not always pleasant.
So as the @op rightly mentioned, it is very important to a have a plan, have a target goal and stick to it, otherwise it will be difficult to make the right decision during that time.