I find the difficulty of curved lines has less to do with the trajectory and more to do with the path it takes. So far all you've done are straight lines that require one simple motion, going from point A to point B. Curves on the other hand don't just go from point A to point B, they do it in a very specific manner.

My advice is to ghost more with curved lines than with straight lines, and when you do pay close attention to the motion your pen is taking instead of focusing mainly on where the line ends.

When it comes to creating that smooth, back-and-forth zigzagging flow, and then matching it once again with another mark, there are a few things that are critically important:

• Drawing with confidence - this doesn't mean drawing as quickly as you can, but shutting off the part of your brain that wants to make a lot of course-corrections. Hesitation will result in wobbling. Of course, the easiest way to draw confidently is to execute the marks more quickly, but that has pretty significant downsides for this exercise. Try to bring that execution speed down, but maintain the confidence.

• Executing the marks from your shoulder is also very important - the shoulder works like the stabilizer you'll find in some digital software - it makes it harder to make little jerking motions that add irregularities to our flow, but also makes it much harder to produce tight turns. Of course, tight turns aren't what we need here - we want to flow languidly, like a meandering river.

For what it's worth, you had a fair bit of success with the arrow in the upper right, specifically the rear section. You only really ran into trouble when you got to the front-most part.

I should also mention that as you're submitting for official critique, you should not be moving onto the next step until the previous one has been critiqued and marked as complete. Critiques can take a few days to come in, but that's also a great opportunity to make sure that you're following the 50% rule.