UPDATED WITH BOSS’ REACTION: Quitting my job and I’m terrified. I need advice, please.

I’ve been working with at this company for two years coming this August. I work one on one with a financial advisor, so the practice is just he and I. We’ve developed a good working relationship and a good friendship. I like my job but knew it was never what I wanted to be doing for the rest of my life.... I just had my baby boy on April 28th. A few days ago I got a message from a recruiter on LinkedIn about a huge opportunity to be a daycare center director. Before I accepted my current job, I was a daycare teacher and then an assistant center director, but went in a different direction to build up my business skill set. I received the message and immediately felt like it was a sign from God. I interviewed on Thursday last week and on Friday they offered me the job. I took the weekend to really think about my options. It’s $15K more than my current job, I get to bring my baby to work with me, don’t have to pay for daycare, and it’s a dream position for me. I accepted, but now have to tell my boss that I’m quitting. I know it’s “just business”, but with our personal relationship I’m just so scared he’ll be so hurt. I was supposed to start back at my job on July 23, so I know I need to tell him ASAP. (I want to give him at least a month’s notice and help him hire someone to fill the position if he’s not too pissed off to accept my help.)

I just don’t know how to go about it or what to say. I’m just so anxious about the whole situation and when I think about it it gives me a migraine or I throw up. I feel this way because while he’s nice to me, I’ve seen the way he gets angry at his clients when they leave his practice. He acts like an absolute child throwing things, yelling, and basically saying, “well, f*#% them.”

HELP.

**UPDATE:

I went to see my boss today. I had practiced my speech in my head a million times. I walked into his office and made a little small talk and then launched into my spiel so I wouldn’t start crying with nerves. I told him I had accepted a position- I told him a recruiter reached out to me and that the job was not something I sought out. I told him it was a dream job and offer and that it was simply just a great fit for my family at this time. I let him know that I would like to help him hire a new assistant and help to train if he’d let me. He said he wasn’t sure if he would. He kept saying, “I just don’t know what to say.” I felt terrible...until he asked me if I expected him to pay me for my last 6 weeks of maternity leave. We had worked out for my maternity leave that I would receive 6 weeks paid. I chose to instead of get 6 weeks full pay over 6 weeks to take 50% pay over 12 weeks. So basically I have been paid half of what we agreed on. I gently reminded him of what we had agreed on but said it was ultimately up to him.... but yeah, that pissed me off. Then we just both kind of awkwardly stood up and I told him to get in touch with me if he needed anything. I have him 1.5 months’ notice.