You are going to be just fine. I think having your first baby is like suddenly landing on another planet... no matter how prepared you think you are, you suddenly realise that you have no idea what is happening. But the second, with the second you have already been to that planet. You are already a mother. You already have parenting skills. You may think you have forgotten all the newborn stuff, but it just does come back to you. Sure you will be tired, but it will pass. It will be busy, but it will also be so much fun. The first time Jack snuggles with his sibling your heart will melt. It will be totally worth it.