I was a practicing Buddhist for several years in the early 2000s and did this - it worked (mostly). The downside was, as you suggest, that I lost my inspiration and personality (and ended up almost broke).
but non-stop mental chatter is a sign of disease -- in that your mind is not at ease.
It once irritated me enough that I ended up in front of some sort of mental health practitioner. They came up with some things that involved taking poisonous metals as a "cure" but I privately went to a meta-cognitive therapist instead.
The result was that I can now "ignore" the errant part of my mind with the more usual, conscious "executive" part (I don't know all the terminology, sorry) but enjoy the fruits and spontaneity of what the uncontrollable side has to offer when I choose. It works, because I couldn't be much happier or productive now! :-)
I spoke with friends who had depression and were taking reasonably pedestrian drugs like Prozac, and while they were "happier" in the typical sense, ultimately they were less satisfied with life because the drugs dampened their vitality in a way they couldn't define.
(I know, a serious overshare, but that's part of the deal ;-) I suspect the majority of people have these sorts of issues at times, but society has entrained most people to keep it under wraps.)