Some newbies are panic when seeing the red portfolio and made the very fatal decision. That is the most common mistake made by most people especially newbie.
Even though pro traders and veteran traders do oftenly loose no matter how they train and work on their strategy it is because trading is really an unpredictable job and no one can perfect it not even you have a lot pointers to follow like the ones that op suggested.
but as what many people said, loosing is just a part of the game. you can just try again and again in order to earn some profit that can lessen your previous losses.