Take backup of your data. Your hard drive will die some day and will take your data along. You might get hit by a virus or malware which will destroy your data. You may lose your computer to theft or other damage.
Keep multiple backups. Online and Offline.
Buy two external hard drives. I recommend Western Digital My Passport. They are good and have built encryption so you can protect entire drive with a password. Install a program called FBackup. It is free. Use it to take backup on these drives. Take this backup manually. On both the drives. You may take the backup daily or weekly, depending upon how frequently you generate new data. FBackup will create exact mirror image of your local file structure on the external drive.
Keep one drive at home and another at your workplace. Keeping multiple drives at different physical locations is necessary in case one of the location is burgled or is destroyed in fire. External drives will also die someday, so multiple backups is must. A photographer lost lifetime of work when all his backup drives were stolen from his home. Avoid a similar fate.
Apart from offline backups, also keep online backups. Get a paid account of any of the online backup services – IDrive, DropBox, OneDrive, Google Drive, iCloud any of them. Take backup of your most important files on them. Online backup is slow. It took me months to upload my 300GB of photos online, but it is worth it.
Do not keep your external backup media attached to your computer all the time. If your external drive supports encryption, use a password to protect it. Do not carry your backup media in your laptop bag along with you everywhere. If you lose your bag, you lose your computer as well as backup.