Everyone breaks a rule occasionally. The marker here is the pattern: you intend to stop and do not, repeatedly, and the intention itself stops having any effect.
It usually appears alongside other signs. Limits are set and passed the same day, sessions extend far beyond planned hours, size decisions are made mid-session and not remembered clearly, and promises to reduce are made to others and broken.
This is the point at which better rules are not the answer, because the rule-following machinery is what has failed. External constraints help - broker-side limits, removing platform access, involving another person - and so does professional support. See problem-gambling-help.
Related: trading-addiction, gambling-disorder-signs, chasing-losses, self-exclusion