Creates a pause
Writing can put a little distance between you and a difficult thought.
WHY IT WORKS
Sometimes the value is not in getting an answer. It is in slowing down enough to put a thought into words and have another person receive it carefully.

Writing can put a little distance between you and a difficult thought.
When thoughts become words, patterns and priorities can become easier to see.
You can respond when you are ready instead of keeping up with a fast conversation.

AT YOUR OWN PACE
There is no requirement to answer immediately, explain everything, or reach a conclusion. The conversation can remain small and simple.
You deserve enough quiet to hear what you are actually trying to say.
The first message does not have to be perfect.