it is all about self control.
some people have it and some people need some help to acheive it.
and for acheiving that you need to try hard sometimes, and this can be putting your funds in a safe and cut it or it can be going out and getting busy with some other activities.
Ya just like you said,this is totally about self control.This is the hard thing in gambling.At first,we just wan to gambling for fun,after that,when we already win a big amount of profit in short of time,we will feel greed and wanted more win.And the result,we will lose all the money we have.