Take care what name you give to the file copy.
If you choose the name of a file that already exists it will be overwritten by the new copy!
Either:
Always use the cp command together with its -i option.
This will prompt you for confirmation whenever the copy would overwrite an existing file.
or
Create a command alias for the cp command.
Including the -i flag in the alias will make sure that you are always prompted for confirmation whenever the copy would overwrite an existing file.