A good trader will not let his account on the platforms grow and grow, because even if make profits, they are still present inside the platform, that is, they are promises or a loan that you deposited on the platform and you are waiting for them to fulfill their obligations and make you withdraw your profits. Make your investment portfolio grow, develop your trading skills, and withdraw your profits first.
While I do agree that the money that goes unused should be withdrawn and not kept there, specially at exchanges that are not that good, I also think that it is no way of growing if you keep on withdrawing. Let's say you started with 100 bucks, and you made trades that are 100 bucks as well, eventually you did so well that you have over a thousand dollars, would that make sense to still keep on trading hundred dollars?
I would suggest that you should increase that, even if you decide not to do a thousand dollars, you could do five hundred or seven hundred dollars trading. So you should always consider maybe using all of the money in the exchange instead of withdrawing it, that could make a lot more sense for you on the long run.