It's a 90s Will Smith reference, and it's a tune. No one? OK, moving on...
What would happen if your hard drive exploded right now? How much of your data would you be able to recover from other sources? If the answer is 'none', then we need to talk. Backup is another of those boring subjects that only becomes of interest the split second after it's too late to do anything about it. To save the aggravation, here's some best practice tips.
Firstly, choose your method of backup. The most straightforward is an external hard drive. They've dropped in price of recent times and you could now get a 1TB (over 1000GB) hard drive for under £80. Windows has some basic backup features built in, but you may find a bit more flexibility in third-party software. I can recommend SyncBack, but try some free demos and find out what works for you.
You may find some on-line solutions work well for you. We've talked about this previously in the context of cloud-computing, but let's refer specifically to email for a second.
For a long time, POP was the way to access your email. Post Office Protocol (no really) means the email is downloaded and kept locally on your computer. Great for offline access but not as useful if anything bad happens to your computer. It is possible to back up POP folders, but even better is to leave the email on your ISP's servers. The key expression to look up is IMAP and although we won't go into it now, it essentially means your computer and email servers stay in sync, while actually storing the emails safely with your email provider. If you lost your hard drive, you could re-download your entire email history on to a new computer.
A second consideration is regularity. Now technically once a year is regular. It rather depends on how much you use your computer as to how often you need to back up. A serious power user, including every business that uses a computer, should be backing up at least once a day. As a casual user your going to have to make a decision. After every session ask yourself what the impact would be if your computer disappeared overnight. If you would consider it disastrous because of the lose of data, then it's time to backup.
Backing up is not optional for any serious - or regularly casual - computer user. There are a myriad methods to do it, all you have to do is do it. And I don't want to worry you, but can I smell something burning?