When developing your own library of code, such as:

• code you are experimenting with or testing
• some code you routinely cut and paste (utilities)
• samples that help illustrate cool solutions (model code)

... you'll want to make improvements as you learn more.

Improvements lead to new problems

Saving something that works at a certain stage--then branching out--is what coding is.

Vesioning is the way preserve your work and stay sane.