Auto-correction is a double-edged sword if I ever saw one. It's great because I'd have an abundance of typos without it, yet it's extremely frustrating (and embarrassing) when it doesn't actually work. Just take a look at the very recent example below from Breaking Bad star Aaron Paul. Funny for us, embarrassing for him.
I have a particularly difficult time typing on small keyboards (i.e. fat-finger syndrome), so disabling auto-correction on my Samsung Galaxy S4 is a no-go. I'm willing to risk a comedic correction every now and then, but what's even better? Toggling it on and off on the fly when you know it will fail you.
The mod works primarily with SwiftKey and the Google Keyboard (but not the themed Google Keyboard), so make sure you're using one of those. Also, since it's an Xposed mod, make sure you're rooted (you can root your GS4 in under two minutes) and install the Xposed Framework to get started.
Open the Xposed app and enter the Downloads section to search for Suggestions Toggle, then slide to the right and install it. Alternatively, you can download the module directly from this link.
Once installed, head back into Xposed and make sure to properly activate the module.
To utilize the mod, simply double-tap any text box to enable/disable auto-correct suggestions. The suggestion bar will disappear until you double-tap the text box again.
While this doesn't yet work on the stock Samsung keyboard on the Galaxy S4, SwiftKey and the Google Keyboard are popular alternatives the mod does work well with.
An update may add more compatibility with other keyboards, but this mod makes it extremely easy to type names or custom slang words, making it so you won't have to go back and edit the unwanted "correct" text.