Okay, so on Monday I talked about a snowball rolling downhill. Today, I found a video to share.
Just notice what happens when a person tries to get in front of it and push it back on course. That is reactionary, rather than building a track to guide the snowball on. My Favorite moment though is when the guy jumps on top of it and almost gets rolled over. See what happens when you try and ride or guide momentum? You need to create the path for it (in this case, I would recommend hay bales), and try to keep it away from obstacles; but a lot of the time, these things have a life of their own.