stewing.....or simmering?

Stewing sounds like I'm thinking about something bad but in reality I have a good option so can I call that simmering? I heard back from my post-doc possibility and they offered to write me a formal offer letter with a flexible start date! So that is exciting but I'm just trying to think about it from all angles. Do I want to go there? (yes I think so) The worry is that I said I would try to be done near December, what if I blow that and take longer and irritate my new boss? What if something happens before then that messes up my data collection time? What if I move E and I out there and I fall flat on my face in a new lab? yikes. It just seems so scary to get a real job. I'm worried I'll disappoint my new boss, making my old boss disappointed at the same time. Am I missing out on other opportunities if I take this one now?

I am very happy to have the offer, to have somewhere to go to, to have a salary and a plan. This way when E finishes his MBA in June he can start to look for jobs early in the new city. I also feel a lot of pressure to finish as fast as possible even though some of the data collection is going slowly and I can't control all the variables that make it crawl along. I can focus on writing up what I can, I can analyze as I go, I can plan out my time and use it efficiently but the technique I use does not guarantee results everytime I use it. That I can't change, I can only keep going. But I have to share sessions w/ my lab partner so I only get 1/2 as many as I need. I can't change that either, he needs to finish too. I'm thrilled I got this chance, but I also feel like someone just gave a giant brick to me while I was already treading water.