Writing can stir up all kinds of memories and feelings, and sometimes despite all your efforts to stay on task (write your story according to how you want it to go), you get so emotional, your need to get closure with a certain person (whoever caused you grief in the past) is so strong, you can’t focus on your writing.
Usually, two things happen.
One, you pour all your distress into your writing, and it can then go sideways or lead you to a dead end, which will frustrate you even more and cause you to rewrite everything later (or not even catch your mistakes until your writing is published, which is even worse).
Two, you walk away from your writing and lose hours or days of work while you deal with the onslaught of emotions, and as a result either get even more stressed out (all that time lost!) or lose interest in your story as time passes, or feel like you want to give up (the worst outcome of all).
There is a third alternative that I’ve learned recently and have been applying to my writing process (while sticking to 12 Columns and to scene blocking and staying on track even when my emotions run a ruckus).
And that is:
Write a letter to that person—the person who has caused you grief.
You don’t have to send it. The point is to get closure—for yourself—so you can move on with your work. It can be a letter written by hand or via an email. Write it all out and DO NOT SEND IT. Put it away, wait, then when you’ve nearly forgotten about it, read it again and decide if you want to send it. Often you’ll come to the conclusion that it’s not a good idea because it won’t change much, and that person doesn’t care and won’t even open it or read it. But it doesn’t matter. What matters is that YOU now feel better and are back to work.
You’ll find this will keep you sane (as sane as we writers manage to get) during your process. It’ll also help keep you calm, and you produce your best work when you’re calm—calm and at peace and happy.