If you understand the current move on a higher time frame perspective, its is not so complicated to take day trades / scalps in the correct direction. This can lead to fast account growth. The issue is that mistakes are inevitably made especially if you are still learning and this is why its important to limit risk. If you don't think its possible to double your account day trading futures why even bother?
I am not talking about taking all your life savings and putting into an account and trying to double that. I am talking about an account size which you determine is sufficient to cover margin and inevitable draw down based on forward testing your ability to read the market. Someone trading $10,000 for 1 ES, or $1,000 for 1 MES should be able to grow the account pretty quickly if they actually know what they are doing.
I never said it was impossible, you said it's not that hard, big difference ...
Anyway, since its not that hard for you i expect you to have easily done it before?