How To Draw Straight Lines
Instead of drawing one long straight line, draw the line bit by bit, using the little ones
Draw a short line, and then extend it a bit...
...and keep pushing it out, further and further. every now and then, stop to check that it looks ok.when you're happy with the line, go over it again
With a bit of practice you'll be able to draw any long line by doing small lines and extending them bit by bit.