I think you hit the nail on the head. Structure is the key.
For most people, a schedule/structure equals accountability. Accountability means that, even if you don't feel like it some days, you'll practice last week's lesson so that you're ready for this week's lesson.
As beginners, many of us, left to our own devices, might play a few scales, and then get about the business of learning our favorite song by tab. We simply don't know what we don't know. We don't know what to practice next. Any structured plan is better than that.
So, even if you don't to that plan, find one and stick to it.