If you are writing for your own use, keep the text as plain as possible. If you then have to re-use the words in something that needs polish for others to look at, you will have less to undo.

Your problem with line breaks has a couple of potential fixes, depending on what you use for a text editor the details will be different. First, you can show "invisible" characters like tabs and linebreaks. Second, you set your default preferences to soft wrap text.

If you have seen really old movies with manual typewriters, what you see for word processing is pretty simple.

1. Insert paper
2. Start typing.
3. Reach the end of the paper.
4. Put your right hand on the lever and pull it to your left. This does two things: (a) turns the platen--the cylinder around which the paper is being carried, like a laser printer drum, so that the paper advances one line (this is a line feed) while (b) you return the moving part of the typewriter that is advancing from left to right so that each new keystroke hits a different column, and that is the carriage return. Fast forward a little and we have an electric typewriter which does the work of line feed and carriage return just by pressing the "return" key.

Now, a thought experiment. What if the paper were arbitrarily wide and the carriage part of the typewriter arbitrarily wide so that you could go on typing indefinitely? At some point, your first words would be out of sight to your left like cell A1 when you're over in cell AH1 in a spreadsheet. Well, that's the analog to having soft wrap off.

With soft wrap on, you have something that is not available in a typewriter without magic, which is that when you run out of room on the right side of the screen (paper), the text just carries over to the left on the next "line." So what looks like a paragraph on the screen is logically just one line, because you haven't pressed return to produce the equivalent of a line feed.

When you do, you start typing on the next logical line, but unless you press return twice, there is no white space between the beginnings of the lines to show the paragraph break. Since it's useful to know where paragraphs start, either use a double return or indent the first line with a tab.

If you have a short hand, use an abbreviation expander. Short hand is much easier to write than to read, so let the machine do that work as you type.