Stress can kill, and for me, the majority of my stress comes from emotions more than my thoughts. I admit that ruminating on negative thoughts leads to negative emotion but I feel that it's emotions that make people impulsive and even self-destructive at times (because if we thought things through then we wouldn't act on impulse and get in trouble in the first place). Sometimes even trying to talk to other people only adds to the stress of everyday life, but addressing an internal issue through writing usually grants new peace of mind that can't be obtained through just talking at times (at least for me anyway).
I believe that writing about how you think instead of just talking about how you feel grants clarity; self-reflection opens your eyes. To see your own words on paper also forces you to "listen to yourself talk". Communication is always a two-way street: speak and listen; and being human, we have to feel through our hearts and think with our minds. Personally, I prefer the latter in both sets and I'll just keep a pen in my hand to do the former as well. Just saying.