it is correct to choose to allocate a certain amount to limit losses or at least have some "rules" ... but is it always possible?
The problem is when you can easily access ancillary funds and then pay more than you owe. If you are in a "rush" during a session or you see an interesting match, it's really easy made this kind of error.
The best trick in this regard is to set a limit on the possible deposits and for those who use sites with crypto, create a cold wallet that is difficult to access (or why not with a timelock to block those funds), even buying collectibles where "locking" value can also be an interesting strategy...