Back to work/nanny

Ja
Any advice for me?? I have been at home with my son since he was born. We've never had a sitter. I've never been away from him for more than 1.5 hours. I am the one that cares for him 100% of the time. I got a new job which will be work from home (praise god) but only after 3 weeks of training in the office. This means being away from each other all day, pumping all day, the whole nine yards. I hired a nanny and we are doing a slow ease of transition before I start. But I'm dreading the whole thing and have a lot of anxiety about leaving him and how he will be without me all day and me without him!! Any suggestions from those who have been there?