How to set a daily stop in dollars, why three planned losses is the right size, and what to do with the itch after you hit it.
Pick a dollar amount. "Minus $300 and I am done" is concrete. "Minus 3%" becomes "3% of what I had this morning, before that one trade, which should not count". Percentages invite negotiation; dollars do not.
If you risk $100 per trade, the daily limit is $300. Three losses in a row is normal variance. Six in a row in one session is you losing the plot, and the limit stops you between those two states, which is exactly where it should.
When the limit is hit, log out. The dangerous trades happen while "just watching for a bit". If the urge to click is unbearable, switch to a paper account with the same chart; the urge usually fades within twenty minutes once nothing is at stake.
Some platforms offer loss limits; most do not advertise them. A trader on tilt is their best customer that day. The limit has to be yours, written down, and respected on the days it feels unnecessary, because those are the days it is working.
A practical way to make it stick: write the limit and the date on a card before the session starts, and write the result next to it when the session ends. After a month you will have a page of days. The days you broke the rule will be the worst days on the page, every time, and seeing that in your own handwriting does more than any argument.
A daily limit stops one bad session. A weekly limit, roughly three daily limits, stops a bad week from becoming a bad month. When the weekly number is hit, the week is over: no trading until Monday, and the Sunday review decides whether the plan or the execution was the problem. Most of the time it was the execution, which is the cheaper thing to fix.