What to expect when trying HRT for the first time

Hey trans fems!! I've had my doses for ages, but I've been too consumed with life to worry about trying them. I just got news that my chapter of life is going to be changing soon, and I really wanted to try them during my current stride. So I've decided that just for one day I'm going to give it a shot to see how it makes my brain feel, and I'm going to do a proper two week test run another time. What can I expect from the first day? Any things to be concerned about? Is it possible that this derails my productivity or something strange for the first day?