So true bro. And rest is an important factor in all of that. Glad to hear it's going well.
I'm also doing some envs studies for now, from what I've learned there are a few things which I think you already got.
One is to focus on the main geometric shapes and composition. You want to nail down the first big shapes and lines, kind of like gestures, but for environment. I've noticed that doing exercices with a time limit for yourself is helpful for this. Also seems the case for others I've seen in the forums.
Once I have my main composition, depending on the time I have, I'll focus on the details of the piece one part at a time I'll break down the image in "main parts" and "not so important parts". For example, maybe the car is important, maybe the stairs are not. It depends on what you want the user to focus on.
Once you identify these priorities, start working on each piece of the "segments" of the piece one at a time. Instead of seeing the piece as a whole, focus on each individual piece depending on it's priority. And here's where depending on your bandwith, you might want to impose a time limit per piece overall. The more time you invest per piece, the more detailed the overall image will be, but make sure your time is mostly spent on focus points, and you can get away with texture or "suggested detail" in parts that are not so important.
Once you start getting into the details, I'd recommend to use references on the important parts. For example, look up some cars and check the details as you work on it.
Personally the biggest challenge is just said time management per component. I tend to obssess a bit, so it's easy to just spend too much time if I don't enforce a time limit for myself. I'll usually manage time depending on the importance of the piece itself. Once I feel it has "met it's purpose", I'm basically done even if there are improvements pending.