Save the Pieces
Whenever you spend time and effort entering program code, word-processing text, or other voluminous data into your computer, be sure to save your work periodically to disk or tape. You should do this as often as every fifteen minutes or so. You won't regret it.
This protects you against loss of the major portion of your work if you lose power or suffer computer lockup. These conditions do occur, and usually at the very worst times.
Good intentions don't count here. You have to do it in order to benefit. A cheap kitchen timer or photo lab timer should be part of your computing paraphenalia. Just start it ticking when you start typing. You'll be surprised how soon it rings.
As you save, alternate the file names so you don't write over your last material. For example, call your first saved piece DOC1, the second save DOC2, the third DOC1 again, etc. This makes sure you always have protection against a "bad" save.
Cassettes for the Atari are notorious for loading problems. When backing up a program on cassette it is wise to save twice on each side (four times in all). Be sure to record the footage counter reading for each save so that you can find the starting places of the various saves.