Teacher here (University), and I still have bad days. That said, preparation goes a long way. Early on, I would design a lecture, record myself doing it by myself, and then rewatch and adjust, practice, record again. Over time, I have seen a lot of improvement, but there are a lot of flavors of blocks, repetitions, elongations, etc. Going on 13 years now, and had a bad day on Monday in class, had a better day on Wednesday... so it balances out, kind of. In terms of teaching, students often prefer more engaging, hands-on activities (be a "guide on the side") instead of basic lectures ("sage on the stage") in a lot of disciplines, so becoming a good teacher is more than fluency. You should, without hesitation, continue your goal to be a teacher. There are so many bad teachers that fell into it because of a lack of motivation to take risks and now hate it, that a passionate teacher will go far... so many rewarding connections and relationships are on the horizon. Best of luck!