Weeks of profit, then one day takes the month away

You had been getting it right. Small, steady, nothing dramatic, and the month was comfortably up. Then one session, and by the close the month was flat or worse. The eighteen days were not an illusion. They were just all smaller than the one day.

Why one day can hold more than a month

A day where everything goes to plan has a ceiling on it, because the size you take when you are calm is the size you decided on. A day that gets away from you has no ceiling, because by the middle of it the size is being chosen by the day.

The steady weeks change what feels normal, too. After a run of them, the position that felt large in the first week feels ordinary in the third. Nothing on the screen marks that change. Your trade book does.

And the day itself rarely starts out as the big one. It starts as an ordinary loss, and then there is another trade, and the number at the end is not something anybody set out to produce. In your own records it looks like this.

• Your worst single day for the month is larger than your best week.
• The quantity you took that day was more than your usual quantity, and you had not planned it before the open.
• The number of trades on that day was well above your usual count.
• You can name the day without looking it up.
• You were up on the month before it and flat or down after it.
• There was no single trade that did it. There were several, close together.

Counting it from your own records

Use your trade-wise profit and loss report rather than the ledger, because ledger entries mix in charges and margin movements and are dated by settlement rather than by the day you traded. Ask it for a date range covering the last three months, and total the rows for each day yourself.

Now three pieces of arithmetic, all of them subtraction. Your largest single-day loss against the total of every up day in that month. How many up days it takes to add back to that one day. And the quantity you held on that day against your usual quantity for the month.

If you have set yourself a limit for a single day, in rupees or as a share of your capital, count how many days in those three months came in past it. The limit is yours. This site does not have one for you and will not offer one.