Letting people know that this is hard for you is a great idea, just so they are not surprised that you’re not feeling to great after a change that they might not have noticed or been bothered by themselves.
That said, the best thing to do to prepare for these situations is to find some items (the smaller the better) that make you feel safe that you can have with you in your purse or backpack at all times. These objects can include small stuffed animals, pictures of your favourite people, or scented lotions (favourite smells are really good for reminding you of good things). That way, when a change happens and you are uncomfortable, you can find your objects and remind yourself of your “happy place”. Once you’re feeling more calm and ready, then you can make a plan to adjust to the change.