Big winning days are often followed by poor days. Common reasons:
Increased size because "the market is easy right now".
Lower standards for entry.
Trading longer than usual.
Approaches that help:
Keep size fixed for the next day regardless of yesterday.
Set a profit-based daily stop: stop after reaching a set gain, or after giving back a set part of it.
Review the big day in the journal: was it the plan, or luck?
On prop accounts with consistency rules, a big day can also be a problem for payout, which is another reason to stop when the day is already good.
One useful check after a big win is to compare the next day's first trade with your plan. Many traders find that the first trade after a strong day is taken earlier and with less confirmation than usual.
After a day that clears 2R early I force the same size the next morning and a hard stop once I give back 0.6R from the open. Without that I have opened larger and earlier, exactly the overconfidence pattern the thread names.
Journaling the big day matters. If half the gain came from one news spike I did not plan, I tag it luck and refuse to treat it as permission for looser entries.
Prop consistency rules make the big day a double edge. Stopping while still green has protected a payout path more than once when a late fade would have skewed the day share.
The first trade the next morning is the tell. I require one extra confirmation versus my normal checklist, which sounds small and has already blocked two weak chase entries.
Do you lock size for the day after a large win, or only cap how long you are allowed to stay online? I lock size and also cap the session at my usual end time.