Managing self-fulfilling prophecies is harder than it sounds, because we have a lot of impulses that make us want to down-spin, that is, to shoot ourselves in the foot, to self-defeat.

But sometimes overthinking is just trying to find intellectual reasons to assert that necessary little bit of faith in yourself that gets you moving in the right direction - the half full vs. half empty decision, and its parallels. There ARE no intellectual reasons to back this process up, though - it's a pure act of will, a fiat (as in 'fiat lux,' let there be light). You have to get used to the idea of doing this one arbitrary thing - having faith in yourself. Not as perfect, but as 'good to go' - competent enough, able to improve, and able to detect mistakes and make good on them.

But here's another thing. With human interactions, they're so complicated that you need to have your 'gut feelings' and intuitive reactions in good working order to get by. Logic, and planning what to say and do, are OK - but they can only get you so far. When you decide to have faith in yourself, it becomes easier to trust yourself in the scary realm of your intuitions, which you can't fully understand. When you need to decide at conversational speed what people's gestures and statements really mean, and how you'll respond, you need to have this whole apparatus of quick understanding - 'sensing' - working for you.

Again, the Christian advice would be to pray and seek the holy spirit's help, so that with grace, your faith in yourself, now partnered with faith in God, can give you access to spiritual inspiration via the holy spirit's counsel.

But even people who turn away from religion can do the basic bootstrapping and accessing of their intuitive skills. I suspect some kinds of genetic constitution such as a predisposition to depression may make it more difficult for some people, but to some extent the whole operation simply runs on logic (specifically, a kind of logic called recursive logic). You don't have to totally understand it to make it work. Just start with that basic belief in yourself and take it from there.