> When your eyes read to the end of a line of text, they have to jump to the beginning of the next one. Left-justified text causes all lines to start at the same vertical, making your eyes sometimes miss the jump and begin reading a wrong line. This is why you're sometimes reading the same line twice by accident. By right-justifying instead, the left edge of the text is made variying, and your eyes have an easier time picking the correct next line.
You actually experience physical pain?