If you're on a traeger or pellet smoker, try cooking with the fat cap down.

Have a water pan in the smoker.

Check periodically to make sure the brisket isn't getting dry--if it is, refill water pan and spritz with apple cider vinegar.

Consider wrapping whenever it's getting very dry or the bark might burn if left in. Once wrapped, you can transfer to oven--it won't be getting any smoke anyway, and it's easier to monitor and adjust temperature.

225 is fairly low for a pellet smoker with brisket. I usually go with 250 on a whole, but you might need to go lower on a flat by itself.

Let the brisket get to 203 or so before removing from heat.

LET. IT. REST. Like an hour /minimum/. Two to three is ideal. The more the meat can rest, the more moisture can be redistributed. Dry meat is often tough meat.