Human nature plays so many tricks on us that exactly when you thing you know yourself and can control your emotions (in trading these are fear and greed) market comes and makes you have second thoughts, makes you having doubts, second guessing, etc, and all your previously trading strategy is gone just like that.
Having a demo account surely helps in terms of analysing past price action and trying to forecast future price movements. However, keep in mind that when you analyze historical data you don’t put fundamentals beside each group of candles you are looking for, not even looking at the time of the day/week the pattern appears. So why taking it into consideration when looking at current price action?
This is the main difference between trading on a live account and trading on a demo account. On a demo account you wait patiently for the take profit order to be hit because in the corner of your mind you know this is just a demo account and all you do is testing a market strategy. On the other hand, when trading on a live account, you may want to take some of your profits earlier because human nature (greed in this case) makes you nervous and all kinds of explanations and excuses will come to your mind in order for your action to be justified. And everything you planned so carefully just goes away.
There are many advantages in trading on a demo account but if you really want to feel the pulse of the market try to trade small on a live account only to get this feeling. Because in the end this is the situation you are going to have to deal with on a daily basis so why not starting to prepare for those conditions.
It is like soldiers that are going to war, they are trained, everything looks nice and well on the training camp, because deep in their minds they know it is just training. But when they are actually going to war, things on the battlefield are different and unexpected situations come all the time.
The same with trading on a demo account: it surely helps in getting you trained, but you will never be fully prepared for what’s out there under the live trading conditions