Before I address the question, one word of caution. When you say you are trying to practice lesson 2/3 material. Are you trying to do that simultaneously? The lessons build on each other and are not meant to be done at the same time. I do suggest going through them in the recommended order and getting feedback along the way, whether from the community or official feedback. I have received great feedback that way and it has helped me.

It sounds like you are on the right track with the observation, you just need "mileage". Just draw. You have to have a lot of wrong before you will get to right. Keep your work, set it aside and look at it after a couple of days or a week. You will be able to see why things are right or wrong more clearly than you can in the moment. You may be doing better than you think.

I think your stress might be coming from wanting a pretty picture. When I showed my wife what I had spent a month doing (lesson 2), I was quick to explain its purpose because lets face it, it doesn't look like much (although the dissections look cool). Drawabox lessons are exercises. Save the pretty picturess for the 50% rule.

If you can be brave, post some of the things you think are a problem here and let people have a look to see if there are any specific areas you could practice.