How did you know you were ready for baby #2?

So, I had my first baby (a girl) 9 months ago. I was convinced I was done, said I wasn’t giving birth again... but now I feel like the baby fever is back. Hubby has mentioned wanting to have another soon. I originally wanted to wait until our daughter was 3 or 4. Now I’m not so sure... how did you know you were ready for #2??