One cannot overstate the importance of backups. And, honestly, it's hard to overstate just how easy it is to back up your data these days. Let's review the options:
Flash drive, USB hard drive, second internal drive, Crashplan, Time Machine, Google Drive, Box, OneDrive, Dropbox, file server -- and that's not even getting into the more mundane CD/DVD area.
The kick is: back up your critical data. Every day. If you spend 5 hours on homework, or a thesis chapter, or a grant application...then turn around and leave your laptop on the bus...there are few feelings quite like it. There are worse feelings: like spending 6 months doing the above and then leaving your laptop on the bus. Or a year. It happens. No backups and you'll wind up shaking, tearing up, and wondering why you didn't back up your data.
So back up your data. It can take a bit of effort but the trick is just to get your data in at least two places. You can copy it manually or you can have software do it for you.
Crashplan: Campus-sponsored Crashplan service offers cloud-based unlimited data backup of up to four computer per $100. Ask your PI to enroll if you're keeping your data on your laptop or desktop and nowhere else. Crashplan Knowledgebase Article
Departmental File Server: We have 50 GB of storage space if you'd like to use it. Backed up nightly too. email@example.com
Departmental Backup Server: We're a little strapped for space on this one but for $100 we can back up a certain amount of data if you're on the wired network.
Box: Unlimited storage. Web interface; *sync options. https://ucdavis.box.com
Google Drive: Unlimited storage. Web interface; *sync options. https://google.com/drive
OneDrive: Unlimited storage. Web interface; *sync options. https://365.ucdavis.edu
Dropbox: Not free but you can look into it. https://dropbox.com
* Note: Synching is not backing up. If you delete a local item that deletion is synched to the cloud and all other devices.