Shifting priorities, especially seemingly random ones, do introduce stress. I'm sure that your reports are feeling it too, and you probably have concerns about how they feel about being ping pong balls in the match. If you are a perfectionist, it's all the harder when you don't think that you have the time to put in the detail work to make something come out "just so".
Communication is so important in all work, but especially when the seas underneath are rough and unpredictable. I don't know if you receive much feedback from above on the hows and whys of what comes your way, but if you do/did, it's something you can live with more easily. You may have to be clear with your boss about what the effects are going to be on the whole picture for you and for your group when these changes happen. If you're just expected to get it all done regardless, well, that comes with being close to the top, too.
About the alcohol, it might have made it comfortable to go home and put your feelings into the bottle, but that's definitely not going to help anything, you already know that. Maybe just putting it down here is going to help you say that it's getting to you, but you can do more, and the latter is up to you to find what works from advice from SR and perhaps from other external sources.
Just make sure that sobriety remains a priority along with your work. I stepped aside from my prior career path to be away from what I knew was too risky for me with respect to the drink. If you are threatened by these circumstances in your work world, you always have other options to consider, being a successful manager.
You will figure it out!