I've just finished week 1, and as I was running it occurred to me that this whole week has been a lot easier than it was when I first started running about 4 years ago, even though my body is just about as unfit as it was then.
I think the difference is a psychological one. Back then, I had NEVER run more than about 1km at a time, and it was in the context of PE lessons, feeling forced into it, and hating every minute, partly because I was being forced. I think that really shaped my attitude to exercise, and when I was first running my thoughts were all along the lines of "I hate this. This is hard. When can I stop. I can't do this". Over time I started to enjoy it, so now starting again, even though my body is unfit, there's not so much of a psychological battle, because I'm expecting to enjoy it and that makes it so much easier. My mind just wonders and I do what the voice tells me without paying attention to what my body feels like.
Anyway, I guess what I'm saying is that if anyone is struggling, it will get easier.