It happens at least once a day, always when I'm right in the middle of working on something important: I accidentally brush the Command+Q combination instead of Command+W to close a browser tab, quitting me out of Chrome. Sigh.
While it's not that annoying to just relaunch a browser and get back to browsing /r/aww, accidentally tapping Command+Q in other apps can give you a little grief, especially if you haven't saved your work in a while. Thankfully, there's a way to prevent yourself from doing this while still retaining the usefulness of Command+Q. (Only quitters remap the key command to something else.)
The app SlowQuitApps does exactly as its name implies. Now, instead of just tapping Command+Q to kill a program, you have to hold Command+Q for a second. A little circular countdown pops up on your screen, closing your app once it completes. That's it.
While this delay will get slightly annoying if you're looking to close a bunch of apps at once, you'll be so much happier when you don't accidentally delete the thing you were working on for the past hour because you prematurely closed the app. Oops.
And, as the utility's developer notes, you can always adjust the "hold" time to whatever you want (in milliseconds), and you can also whitelist specific apps so they're shut down as soon as you press Command+Q — no delay needed.
If you think you'll be tweaking the app's settings, I recommend installing it via Homebrew, which will make the process a lot easier. If you're already brewin', just pull up Terminal and type in:
$ brew tap dteoh/sqa
$ brew cask install slowquitapps