Ah, revisions. The bane of many a writer, not so much for me. I don't mind being told something needs fixing by my editor. First of all, I trust her judgment and I've learned that when she says something needs fixing, it does. And I also know that by the time I've sent in my manucript, my own judgment is suspect. I've lived with the story and characters for so long, I think everything is perfectly obvious. It takes a fresh look to point out things like the lack of clarity for the heroine's decision to avoid marriage (oh oh!).
So how do I handle something like that? Some people might write a whole new scene, and in fact, in the first couple of drafts of this story, I had a prologue about the heroine and her family that would have made her reasons for not wanting to marry quite clear. Then I cut it, because it started off the story in a very dark place. I wanted the first meeting between the hero and heroine to be "lighter," so that the hero realizes that if the heroine seems aloof and cold later, that may not be the "real" her -- and it isn't. I still think that was the right decision, so I'm not going to simply stick that back in.
Nor am I going to write a whole new scene. Where would I put it? That would affect plot and pacing, and might bring the story to a screeching halt while fairly screaming Character Motivation: Margaret Explains It All For You! Not good.
What I'm doing instead is looking for little "opportunities," as I think of them, to insert small pieces of backstory that will add up to a plausible motivation. Giving hints and little flashbacks. I'm talking about a sentence or two, possibly a paragraph, but no more so I don't slow the pacing.
One thing that's extra nice about this revision experience is that I have plenty of time, so that the rest of my life doesn't have to come to a screeching halt. For instance, yesterday, I worked a couple of hours on the revisions in the morning, then spent the afternoon (finally) getting the front garden in shape. My kids and I ripped out all the old periwinkle (much of it being sent off to a good home at my sister's), then planted new and different perennials, some annuals, a shrub and a tree. Looks mighty nice if I do say so myself. If I'd only had a week or two to do the revisions? No way. Well, maybe way, but I would have been plenty stressed. Since I have more time, I'm a much less stressed-out writer, which is just the way I like it.