/ic/ - Artwork/Critique

I think I understand the exercise well enough: That vanishing points are moved and lines get shorter (but not proportionally) when the box is rotated. And that we can use neighboring lines to estimate the vanishing point, because manually drawing it would take an absurd amount of time.
And I get that this is hard.
But my problem is that I cannot make a straight line or even ghost a straight line unless it's short (but not too short or I draw with my wrist) and at a 15-40 degree angle.

Should I be concerned with that at this point? Should I be grinding the Dynamic Sketching exercise but with different lengths and angles to be able to draw? Or should I just transform/turn the page to get an angle I can actually draw, and worry later?