This is similar to the video which mentioned a boat near a waterfall. The principle is that there is an edge, and you need to do what you can to stay as far away from it as possible. The question should never be "how far can I go?" Or, as John Bytheway rephrased that in one of his talks, that's asking "How bad can I be?" Don't do anything that will take you closer to the edge. Set up personal boundaries, pray about them, and then live them.
But there was one thing I realized today that people need to see. No where do those lessons tell you to not drive the stagecoach, or ride in the boat. Physical attraction is natural and expressing those feelings can be a beautiful part of a relationship. However, the physical expression should not be the main focus of any relationship (before or after marriage), and there should be limits and boundaries before marriage to keep the relationship in a safe place--safe spiritually and physically, as well as keeping the relationship from being focused on the wrong thing. But there still should be some kind of expression. It is not bad to hold hands, or to genuinely and lovingly show other forms of affection. I think it's a really good thing to know if the physical attraction and chemistry is present in a relationship. So include physical affection. But don't get carried away. Don't get yourself confused. Don't cross boundaries. And don't get close to the edge.