I have to make a conscious effort to silence my inner monologue sometimes, after a busy day I sometimes can't stop my mind from chattering at night and can't sleep but I think this is fairly normal.
I like having an inner monologue but agree it make you too slow and methodic sometimes, especially in social situations.
I noticed a while ago that sometimes there's 2 types of conversation; one where you just show the other person how easy you are to talk to by talking about everyday/ordinary stuff - whatevers on you mind basically and the other is more deep, personal or complicated stuff.
I have to remind myself to do the ordinary, everyday one a lot of the time?
EDIT; also when I'm trying to sleep I've noticed when my mind becomes quiet/no inner monologue and you start to see pictures/images without thinking or forcing them to appear, that's when I drift off/fall asleep easily. So I try and concentrate on quieting the monologue and waiting for the pictures to come - does that sound a bit nuts?