Your finger is poised above the Enter key. A nagging sense of familiarity. Yes - definitely a recent one. Why would you waste the full value of a Wordle guess on a previous solution (unless desperate)? Backspace! Over days and months the scenario recurs, but each time you're less certain. It haunts you. So you make a list of previous Wordles (cheaty? no! why should you memorise them? it's not a memory game! :D Check against it each time, by eyeball, then by searching as it lengthens...Ctrl+F, typing, Enter...each doggone time. It breaks the flow :(
So here's a small program, which can run on Java-enabled computers, that pops up an alert if you type a five-letter word that has been a previous Wordle solution, before you press Enter. Backspace removes letters one-at-a-time just like for the Wordle entry field. After each entry (if there hasn't been a backspace, as might happen if you enter a word rejected by Wordle and need to re-type), it resets and processes the next set of keystrokes.
The latest version can be downloaded from the following Google Drive
To run, extract the zipped folder and then double click on the "NotAgain" executable file within; the "lib" subfolder at the same level and the text file containing past Wordle solutions are also needed, but all three items can be moved elsewhere as long as they are kept at the same level in the original or folder or another location. In addition to fixing inevitable bugs, and looking for ways around limitations (inc. ), I may include further features and tweaks in future versions.
Latest source code can be found here. I had in the past also uploaded previous iterations and some notes but that became too messy and has since been superceded by a GitHub page.
Footnotes (re limitations, known issues etc.):
 "But I play on a phone!", I hear you protest. That's on my radar, though I need to investigate, a lot (...perhaps a web-based solution could cover all platforms?)
[2a] The program used to work with a file containing the full list of Wordle solutions, reading up to the previous day's word*. However in Dec 2022 the New York Times decided that future solution use would be 'curated' and no longer follow the fixed order of the original list. For this reason, I can only provide a list of previous solutions up to the point of this upload, 13 Dec 2022, and users will have to update it with 'new previous solutions' as they go for full checking. Words can be added anywhere as long as they are seperated from other text by at least one space or any non-letter character; the current list is in the form of one word per line, with the most recent solution at the bottom, so for look-back clarity it would be best to keep that format. If you miss some days, lists of previous solutions can be found online, e.g. at https://wordfinder.yourdictionary.com/wordle/answers/. (*The part of the code that used to make sure solutions were only up to that point is now redundant, but does not interfere with the new usage.)
[2b] Note that if you have left the Wordle browser open across a 'day transition' (through midnight) to continue working on what is now 'yesterday's puzzle', closing and reopening NotAgain will load that solution and warn it's a previous solution...so best to keep the browser page and program in sync!
 At least, if you wait for the alternative message, ":) not a repeat :)" to appear in the main display area after the word. This will happen instantly, unless there is a delay in processing, in which case it would be best to wait until one or other message appears.
 Latest version (221120_1420) has a small tweak to allow it's use of the solutions text file to be case-independent.
 Since a keylogger is involved, you may get a warning from your system about malware (as I did); there is nothing malicious involved, but I realise this may put off many potential users.
 Note that the program cannot distinguish between keystrokes made in the Wordle website interface and those in any other contexts, or independantly detect which letters are present there. Therefore, if using your computer for other input (e.g. another browser tab, a text document) between Wordle guesses you can get a mismatch between Wordle and NotAgain display. In that case, just backspace and re-type as necessary to realign. Alternatively, use the Pause feature before leaving Wordle, then Restart when returning. (Alao, in the unlikely event that you press backspace after entering a word accepted by Wordle, NotAgain will delete from the existing word in its display rather than starting a new word, so backspace all the way to clear letters to sync with Wordle.) If I find a way around these limitations I will re-code; again, a web-based alternative might help...perhaps making an altered version of the Wordle page that could be played offline-only.