As long as we're doing the wall drill, make sure to do it with the critical post-beginner detail: your standing knee must not develop more than a tiny bit ahead of your standing hip, rather as you flex into the knee your standing shoulder and hip must move forward to stay over the knee. Hard, isn't it? Especially hard to do it without falling into the step. But that's what seperates the men from the boys - and makes keeping the free foot in your own space so much simpler.
The way to avoid falling is to not lower until you are ready to move, perhaps even a tiny bit behind the beat - then you can push out of the standing leg without hesitation, so that the movement is controlled, and rather than falling onto the free leg. This does conflict with the over emphasis on lowering given to beginners who tend to forget to lower at all, so it's a detail that can be saved for a few months later, but it's a necessary component of fully developed dancing.
And of course it applies to the forward action only - going backwards, the knee and hip initially move in opposition.