How do you ever really know that you're ready for child #2

Lately me and my so have been thinking about having another child. Our dd is 2 1/2 and is just about potty trained, she sleeps in her room in her own bed, has been off the "baba" a long while. She's also a great talker, and seems older than her age. But besides the fact... I am a full time practical nursing student.. I have 13 months left of school... Which is not too much aid a big deal (I'd only have 3-4 months of school left when baby gets here). Then also is all the physical and emotional changes that I'm nervous about going through again. And the thought of one sided attention... Jealousy.. Etc. So how did you know you were ready for child #2???