Hi Jadw,
my own experience is that this is sometimes hard to do. For example, I can't learn to drive, mainly because the stress of being behind the wheel (I'm dyspraxic) kicks off hallucinations. I might know perfectly well that there isn't a horse or a small child right in front of the car, but I'm still going to break when an image like that flashes across. And the one time I think "hallucination" and don't break, it might be real.
Today I've had some mild episodes, and I've been able to ignore them, though they are deeply annoying. I've heard the voice of someone who bullied me talking about me, calling me horrible names, and sneering at me. The only time it stopped was when I started practicing my guitar. While I know that she's not there, she's not really talking about me, and her opinion counts for nothing anyway, it's still upsetting to have a running commentary in your head. You can't help but react to it, at least emotionally. I know what's started it though, and hopefully things will ease off as I deal with the stressful situation.
And that's at the mild end. When hallucinations "take on flesh and walk among us" then it becomes impossible to ignore them.