Now… now…
Definition 1 of 2
Pro Tip 1/3Calming Down
Used to soothe someone who is upset or overreacting to a situation. 
Now, now, we can resolve this without arguing.
Pro Tip 2/3Patience Reminder
Said to remind someone to wait calmly for something. 
Now, now, the bus will be here soon, just be patient.
Pro Tip 3/3Lessen Urgency
Implies that there's no immediate hurry for an action. 
Now, now, let's think this through before making a decision.