For me, I only used the demo account to learn how to place orders and how to read charts. Once i understood those two, i switched to a real account with real money. I opened a micro account (some brokers call it a cent account) which is meant for trading very small amounts of money; this ensured i only lost little sums when i got a trade wrong.
Why did i switch to a real account so early? Well, because when learning with real money the emotions are present & intense unike the demo account which uses fake cash so you can take your losses for granted.
Mistakes made on a real account lead to real losses which teach you a longer lasting lesson and you try not to repeat them again, because you know the consequence will be loss of real money.
In a nutshell, there is no emotion when trading with a demo account but when trading with a real account you experience the emotions of fear, greed, hope, etc. and it is your ability to control these emotions that will eventually determine your success as a trader.