My story, “Shades of Red” is available free at the Pittsburgh Flash Fiction Gazette. What do you imagine happened to the characters after the end of the story? Let me know in the comments!
http://pittsburghflashfictiongazette.net/sexy-fiction-shades-of-red-by-nicci-haydon/
Also, if you have a thing for panties (this post ought to enlighten you) then this story is definitely for you!
Nicci Haydon 
God no
Certainly Tracy in the story doesn’t seem to be a very happy person. She’s “the other woman” but seems to be almost trapped in the affair.
Do you think there’s ever an excuse though? Is Tracy in the wrong, or is it only Jon who’s the one “cheating”?
The people who participate do so consciously and do so because of their inability to work on a marriage properly , low self esteem, and personal insecurities. No one puts a gun to their head to do so.
I understand your point – it’s a decision that’s been made, not something that just happens by accident or something that’s somebody else’s fault. Certainly, those involved are the only ones responsible for what’s going on. In the story, Tracy and Jon have met up to continue their affair. There’s no suggestion of ending it.
But is it low self esteem, as you point out, that keeps Tracy in this position when it’s clear that she’s never going to be more than the mistress? I certainly wouldn’t want to judge her (or anyone else in real life in that position). Is she in love with Jon? Does it even change things if she is? She’s still chosen to have the affair.
And what about him? He clearly doesn’t want this to be anything more than an affair. How did it start? There are questions left unanswered, but again does that change anything? There may be reasons, but are they valid?