In fact it is very important to trade with perfect lot size. Most trader are not aware of it. They try big lot most of the time. Sometime they try 1$ lot only with 10$ account where leverage is 1:1000. Sometime they get good profit too from only 20-30 pips. Actually it is a big mistake. You need to know the right things about lot size of a trade. If you maintain money management strictly then you may try little higher lots sometimes.But we should not take risk per trade more than 2% and need to create the lot size based on that risk.