I can never give myself more credit for my lines with digital art! The art program I use (Paint Tool SAI) actually has this feature called a stabilizer that helps keep my lines more steady! And, in general, the line with with the program is smooth and beautiful! Same with Manga Studio!

Though, if a program an artist uses has no stabilizer (and even then, I use this same tactic when I draw traditionally), instead of doing long, continuous stroked to get a straight line, quicker strokes of lines that begin over one another usually help give satisfied linework much more quicker!

Ah, I can’t explain it well, but I’d actually appoint folks to this video to kind of get understanding of what I mean! 

Notice how even with a program that has no stabilizer (Photoshop, in this case), giving a couple of continuous strokes that could be fairly short can make for a straighter line, compared to if you try to go for a long stroke and your hand is bound to wiggle a bit and cause squiggles/bumps.

Of course, everyone is different (as I know of some artists who actually can make clean/smooth lines without a stabilizer in just one go), but it takes experimenting to see if any of these different tactics work best for you! c: