It takes practice to draw what you intend to draw. A straight line parallel to another line, a curve left to right at the angle you wish, lines at different angles without turning your paper (yes, I know you do). My line control is much better since I started actively practicing. I didn't really consider it "practice" until I realized, a year later, that my line control & precision had vastly improved!
sketch the lines of a white kitchen
draw a teapot
design your own silverware
use old patterns to practice drawing lines
add detail to your favorite drawing patterns
draw the lines of the facade of a house (here's my attempt)
practice drawing fonts
learn to draw a fish, then draw fish with different patterns
design the cover of an imaginary or real book
At myinkblog, 48 Beautifully Designed Vintage Websites gives a taste of vintage design, describing the design elements incorporated in the style.
Thoughts on improving your skill:
- Consider doing creative work freehand to build confidence, strengthen your arm, and improve the ability to control the pen.
- Watch yourself. Is it easier to draw when sitting on the couch with the journal to your right, on your lap, on a table in front of you, standing and leaning on a counter?
- When you are drawing and getting frustrated. STOP.
- If your hand/arm is tired, take a few days off.