Answer
Daya (mercy) and Karuna (compassion) are emotions. It is not necessary that action accompanies them. For example, you are going somewhere and you see a person in distress. Upon seeing them, you feel daya; a sentiment of karuna awakens in your mind. However, this feeling remains confined to your mind alone. It does not translate into any action, because despite experiencing the emotions of daya and karuna, you moved on without offering any help.
Kripa (grace) occurs when daya and karuna are transformed into action. Had you stopped and helped that person, had you relieved their suffering, then it would not have been merely daya and karuna — it would have been kripa upon that person. When you bestow kripa upon others, Ishvara (God) also bestows His kripa upon you.