Being "thrown off guard" is a feeling we all experience at some point in our lives. It's the sudden shift in our comfortable state or the unexpected circumstances that catch us off guard. To convey this emotion with more nuance, there are various synonyms that you can use, such as shocked, startled, surprised, astounded, flabbergasted, taken aback, caught off guard, or blindsided. These words can help express the intensity or extent of the feeling, whether it's simply being caught by surprise by a friend jumping out at you, or being completely overwhelmed by a sudden life-changing event. Using a diverse vocabulary can help you communicate more effectively and clearly convey how you feel.