Consistent earnings can only be achieved through proper risk management. Even then, not every trade is successful. Anyone who is successful in every trade is lying. No exception. However, I currently have a high success rate. 

If you bring me a system that guarantees me 1% profit every day, I can tell you that I can find a customer who will pay $1 billion for it in a short period of time. From this statement, you can understand how important these underestimated rates are. 

Check "Dimishing returns".

I looked into diminishing returns but didn’t fully get how it works in trading. It seems like the more you invest, the less you gain after a point. Could you explain why that happens and how to spot it?

Designs pixels, trades pips, and somehow finds time for self-improvement in between.

You got it right. The larger the capital, the lower the rate of return. So you can't make your 2billion dollars 100x. The money needed for that will be much more, so your earnings will decrease.