I haven't done any mountain biking in years and don't have a 29er. So possibly this won't help at all. But I used to ride with kids a lot and we always had to remind them to "look where you want to go." To me this was more important for mountain biking than for road cycling -- I would find myself fixating on the obstacles I wanted to avoid (like the two trees on either side of the narrow trail) rather than the actual trail that I wanted to follow.

And yes practice is important. Sometimes it can help to keep trying the thing you're having trouble with over and over. Go through the turn, stop, go back, go through it again.