it took my breath away

It took my breath away is another way to say that something has happened which was so surprising and astounding, it overwhelmed this person. This is often most true in the case of beauty, grandeur or a similar situation in which the person seeing this beauty or act, was so startled and in awe of it, that they momentarily forgot to breathe due to the immense surprise. It is also a way of exaggerating how much you enjoyed seeing something.