Early extension (standing up too soon in the downswing) plagues a very large percentage of golfers I teach on a daily basis. Anyone from your basic beginner who claims they "didn't keep their head down" to a high level player who claims to have "come out of" the shot could be suffering from early extension.
In this video, I do my best to go over the true causes of early extension and the proper way of going about fixing it. Most commonly, I've heard people telling their early extenders to "stay down" and "keep their butt back." In other words, treat the symptoms of early extension. In my opinion, this video should get more to the root cause of your issues.
In this video I focused on the "steepening" action in transition. One thing I didn't quite hit on is that the shaft can be in the act of shallowing from an "across the line" position at the top but still be to steep in early transition.
I apologize for the low volume. I'll work on that in my coming videos. As always, thanks for watching.