My latest painting

[ChantalFournier]

An example of lost edge would be that given that the light comes completely from the left, there is no reason that we see shade on the left side of the pants. In that case, the edge between the pants and background could be almost lost. Also, there should be occlusion shadow where the character's butt touches the floor, that would make that edge way softer because of the shadow on the floor and the shadow on the pants. You should look at reference pics of cigarette smoke, they are a great blend of hard and soft edges all in the same objects, they curl and swirl and almost disappear and then bam, hard edge.

I think it would be a good idea to work from reference for your next try, because reality is a great teacher.