Did you want a nice, pat ending about Jonathan and Monica riding off into the sunset?
Did you want rainbows and stars? All soft filters and violins?
They're not fighting over who cleans the bathroom or whose turn it is to cook dinner. They were never destined for simple contentment.
Monica almost committed murder for Jonathan. She almost tore them apart to save him. How do you get back on the horse when nothing is the same? Nothing.
They've earned their happily ever after. Now they have to survive it.