As a software developer, I learned about the value of version control over time. My first forays into development were as a child, where I made a single backup of my code on a separate floppy disk in the event I had an issue. This was my one-man-wolf-pack version control system, and it served me well, although it wasn't efficient. In a few of my early development positions, we zipped up all our code each night to a separate folder, giving us the pentagram-version-control system. This worked as long as we didn't need to go back over a week, but it still wasn't very efficient. I think that because we worked on fairly small projects and could hold most of the code in our minds, we muddled through issues.
Later I was introduced to a real version control system (VCS), Visual SourceSafe. Some of you cringe, but that system worked well. We could see the differences in code, and over time I learned to cut loose with my development, just trying new things, knowing that I could easily revert code backwards without much effort. Since then I've worked a bit with Subversion and Git, both of which seem to be very capable, mature systems. I still plan on getting some work done with Mercurial and TFS at some point, just to compare the features and functions.
I started source controlling my databases after reading an article by Bill Wunder. This was over a decade ago, and it seemed to make sense to me. All of the things I had learned about VCS worked with databases as well, and I learned that having a database under VCS provided me with some stability in development, including the ability to roll back to previous versions of code when we found bugs. Trust me, checking out a previous version of a stored procedure is much, much less stressful than restoring an old backup just to look at stored procedure code.
These days I see more and more people putting their databases under version control, which is comforting. It makes me think that we, as data professionals, are maturing in our industry. However there are still lots of people out there that don't use a VCS for their database (DDL) code. Some don't even use a VCS for their application code.
There's no excuse these days. Subversion and Git are free and open source. Download them, spend a few days, and get control of your code. All of the ways in which you can improve the efficiency and quality of your software start with more knowledge, and a bit of version control on which to apply your craft.