I don't think the hard vs soft thing needs to be obvious, it can be relative. Like in Abbie's painting. A lot of it is soft but comparatively speaking there's a distinct edge where the horse's head and the woman's arm meet. It's not a real hard edge but compared to the rest of the painting it's a more distinct edge and is very appropriate since it's right in the focal area. I like that there are lost edges between the hair on both the horse and the woman that get lost against the background, in fact I think it might look just a bit better with more of that.
Here's a less obvious example of one of mine.
I don't claim to be great at this but sometimes I actually remember to keep it in mind. Most of this painting is relatively soft edges, but it gets more soft as you go farther in the distance, with one exception, the main tree. I wanted that to be my focal point. The foliage is still fairly soft edge, it is a tree after all, but it's relatively sharper compared to the other background foliage, but the biggie is that it has the one real hard edge in the whole painting, the tree trunk. That edge is not only the hardest in the painting, it also creates the spot of highest contrast.