Discipline is exactly what you're seeing. Discipline doesn't mean walking. It means waiting for what you think is your pitch, and swinging aggressively at it. Won't always hit it, and when you do hit it, it is sometimes going to wind up an out. But you still have to take that hard, aggressive swing every time you get your pitch.
What you can't do is what a player like Juan Fransisco does, which is swing wildly, without having first selected the pitch.