Don't worry about it. You will get distracted, and it's fine. In mindfulness the clue is to just "notice" whatever the intrusive thought (or whatever) is, then resume whatever you were doing. I found it helpful to do the "breath focus" thing and counting them - lost count all the time because that isn't really the point, it's just something to do while essentially waiting for your brain to do something. Noticing is the point, both whatever you're doing and what your brain does when it veers off.