Just a note from a mom who has been there. My first 2 are 16.5 months apart. I had another 17 months later. It is tough, but not terrible. You just do it, like you did when you had one baby.
The best thing was that Celeste LOVED Lydia. There was never any rivalry or jealousy because Celeste was just to young to have those feelings. I had to watch very closely because Celeste did want to hold Lydia all the time. I had a bassinet, and that wasz off limits to Celeste. I gave her plenty of time with Lydia, holding and burping and snuggling, but when lydia was in the bassinet, Celeste was not allowed to bother her.