You must do it. You must do it regularly, automatically and securely. If you don't do it, you will lose stuff. If you do it informally, you will lose stuff. The stuff you'll lose is usually the most important, current, vital stuff you have.
Regularly: if you back up every now and then, when the inevitable failure happens you'll lose a random, variable amount of stuff.
Automatically: if you rely on human memory to accomplish your backups, when the inevitable failure happens you'll lose a random, variable amount of stuff.
Securely: this is where it gets tricky. Is a backup to a local hard drive sitting next to your computer secure? No. Is a backup to the cloud secure? Unless you're working with us, probably not secure enough.
This is one of those areas of I/T where you really should not go it alone - where the experience to ask the right questions is so very important, and the skill and experience to get it right is vital - where the risk is as high as it gets.
Ask us. We know!