Some people even have specific strategies depending on how much they have earned or how much they lost. For example: if you loose 10€ then you can bet an specific amount that will give you a break even for the last week. If you are in profit you can gamble for example only with your profit so it is impossible to go into a negative balance from this moment on.
Everybody needs to have their own strategy but the general rule is always to only gamble with money that you are willing to lose. It is good to have a plan when you are losing or winning but you need to stick to it.
At some moments, you will start tilting and then it can really go wrong.
Because with a formidable spendable amount, you can make an accurate decision on how much you are ready to wager with, and you will not be influenced by any external factors such as chasing winning or trying to recover the loss.
