Congratulations for completing the 250 Box Challenge!

I can see you made some good improvement with the quality of your mark making. Your lines steadily become straighter and more confident looking as you progressed through the challenge. You drew your boxes at a pretty good size and with a variety of orientations and foreshortening. You also start to do a better job of getting your sets of parallel lines to converge more consistently towards their shared vanishing points!

I would recommend that you try adding extra line weight to your boxes as a permanent step for your future warm ups. When you go to add weight to a line it is important that you treat the added weight the same way you would a brand new line. That means taking your time to plan and ghost through your mark so that when you go to execute your extra line weight, it is done confidently and so that it blends seamlessly with your original mark. This will allow you to create more subtle and clean looking weight to your lines that reinforces the illusion of solidity in your boxes/forms. Extra line weight should be applied to the silhouette of your boxes, as shown here. I recommend that you try adding your extra line weight in no more than 1-2 pases so that you can easily identify mistakes in your work. This diagram should help also you better understand how to properly apply your extra line weight.

Finally while your converges do improve overall I think this diagram will help you as well. When you are looking at your sets of lines you want to be focusing only on the lines that share a vanishing point. This does not include lines that share a corner or a plane, only lines that converge towards the same vanishing point. Now when you think of those lines, including those that have not been drawn, you can think about the angles from which they leave the vanishing point. Usually the middle lines have a small angle between them, and this angle will become negligible by the time they reach the box. This can serve as a useful hint.

Congrats again and good luck with lesson 2!