Sounds like perhaps there's a lack of trust in oneself? Most of us can blink, breathe or walk down the street perfectly fine without thinking twice about it, and whether or not we're paying close attention - it should have no bearing on our ability to do them. Why? Maybe it's because we have no bad history or terrible experiences with which we convince ourselves we're somehow incapable. I think speaking ability is a similar game, but some of us allow each little stumble to leave such a painfully memorable scar. We take something that ought to be trivial and we give it the power to cripple us, because deep down inside, we've bought into the lie that we aren't good enough. If we just believe in our own ability to speak (no convincing or self-talk necessary, just a simple belief in what's true), in the same way we know we're perfectly capable of tying our shoes or drinking a glass of water - we may find that fluency was there all along, we just needed to let go and let it happen (easier said than done, of course).