Actually there are many reasons .., one of them is: Trading using funds for daily needs or borrowed funds.
By using funds for daily needs, it means that traders are required not to lose so that the emotional involvement will be much greater than if using funds that are not being used. It is not uncommon for traders to use borrowed funds or credit cards so that they will mentally add to the burden if they experience a loss.
To avoid the influence of negative emotions that can be fatal, so if you cannot accept the fact that you will very likely experience losses, you should practice on a demo account until you really understand that risk cannot be separated from trading. Using funds for daily needs or borrowed funds will be very risky so many traders feel like they have failed and leave the trading world.