I suspect not enough fat
Are you doing a full packer style brisket or a trimmed flat? What's the weight?
Remember to give yourself plenty of leeway time wise so you aren't left with hungry guests and a brisket that's taking longer than expected.
Cut your brisket across the grain. The point can be sliced, pulled or cut into cubes, reseasoned and put back on the smoker to make "burnt ends". These are fantastic.
You can use a nice sharp knife but wait until the meat has cooled enough to handle. I personally like to take my brisket to 200-205 before slicing.
Try not to open the door much during cooking as there is recovery time associated with each time you peek inside. You might need to add 30-40 min each time you open the door. I fill the water pan with boiling water to help with this recovery time.
A wired probe thermometer set into the thickest part of the meat is essential for you to know where you're at without having to open the smoker to check.
Have fun and remember to post pictures if you can. We all love pictures.