The maximum you can withdraw in profit per day, and per trade, is $10,000. Once you hit this limit, any open trades will be automatically closed, and any profit beyond $10,000 will be removed from your account. This is recalculated daily at 00:30 UTC, based on your account balance at that time.
This rule is in place to prevent high-risk or gambling-style behavior.
Note: Trades opened or closed around the same time, even if in parts, will be treated as one trade for this limit.