The phrase "curdling the blood" is typically used to describe a feeling of fear or horror that makes your blood feel cold or congealed. Some antonyms for this phrase could include "warming the heart," "enlivening the soul," or "filling with joy." These phrases connote feelings of happiness, comfort, and positivity, which are the opposite of the negative and uncomfortable feeling brought on by "curdling the blood." Other antonyms could include "calming the nerves," "soothing the spirit," or "lightening the mood." These phrases suggest a sense of ease and relaxation, which is the opposite of the tense and uneasy feeling associated with "curdling the blood.