Many traders and their trading accounts have succumb to the antics of these firms. As a day trader, keep one thing in mind.
Day trading is war.
It is a never ending battle against some of the biggest trading houses in the world. I want to reiterate that market makers want your money, and will stop at nothing. The will do whatever it takes to influence you into making buy and sell decisions. Your number one best advantage is to learn and understand the movements of the market makers, so that at least you will have a basic fighting chance to maneuver your way through the never ending maze of volatility created by their actions. Level II is purely suppy and demand based.