You lose your trades or even account when you ignore some facts.
First: If you put a trade and keep it watching every second; then its means emotions are high and possibly you are going to lose because you close your trade when it move few pips against you, thinking to save big loss. But at the end you lose and that smaller loss collectively blow your account.
Second: Your lot size ( ) plays important role in profit and lose. Most of the traders lose their account because of that. At first they put high lot thinking to make big profit but when it go few pips in wrong direction they close their trade, as a result they lose.
So if you want to make money and you want to trade profitably then first thing you have to do is build your confidence & control your emotion. Both can be controlled with using smaller lot size at first. Use small at first which you can easily bear to lose without getting into depression and then increase it steadily!
Even if you are trading 15min, you will have to give proper time to your trade. So after analyzing & putting a trade right position and putting proper stop and target level.. leave it.
REMEMBER: Never Go hasty, Never use high if you can bear and NEVER EVER let your Emotion Overcome you!