Breath

If you are able to see your breath in a dream and it does not appear to be cold, consider what you are about to reveal in waking life. This doesn't mean disclose it verbally, it refers to something you will declare with your own actions or choices. Your subconscious mind is calling attention to what might come out of you before you've had the chance to divulge something.
If your breath is heavy or shallow, consider what kind of air you've been taking in and what type of people you have been surrounding yourself with.
Having trouble with your breath is a symbol of stale air, ideas, people, or situations.