At any point, you can download all of your data in a .CSV format, including all of your contacts, gifts, pledges, tasks, interactions, groups, and configurations like your yearly gift goal and pledge goals.
Downloading your data is easy. Here's how:
Click on "Settings"
Click the button that says "Download My Data" underneath the heading "Sync" and the subheading "Download Account Backup"
A spreadsheet in .CSV format will download to your computer with all your data.