When a Sims 4 game update happens, depending on what is changed, mods can break. Unfortunately, there isn't anything you can do to prevent this. However, you can do some things to ensure the update process goes smoothly.
Before you update your game, move your mods folder to the desktop or USB for safekeeping.
Keep an eye on the Deaderpool Discord Server and Scarlet's SimVIP Broken/Updated Mod Tracker to learn what mods broke in the recent update.
Keep an eye on the patch notes. Mods are usually disabled only for bigger updates, not for things like Sim Deliveries.
If careers break, you will most likely need to wait for Neia's career tool to be updated before the creator can update it.
CC typically doesn't break, however, if it does, then it is usually a whole category (for example, eyes, or windows). EA sometimes releases a fix, depending on what was broken, or S4Studio will release a batch fix solve in an update.
The only way to fix outdated mods is to wait for the creator to release an updated version. When the update is released, you will need to re-install/update the mod the same way you downloaded it (see How to install mods).
For this example, I will be updating using UI Cheats Extension, however, the instructions are the same for all mod updates.
Locate your mods folder, Documents > Electronic Arts > Sims 4 > Mods
Locate the mod(s) that need to be updated, UI_Cheats_Extension_Scripts.ts4script and UI_Cheats_Extension.package. Some creators keep the version ID in the title, so to be on the safe side, I delete the old version rather than just swapping the new one in.
Go ahead and delete all outdated files.
Delete your localthumbcache.package (instructions here)
Visit the site for the UI Cheats Extension and download the updated version.
This downloads as a Zip file, so just double click on it.
Grab the UI_Cheats_Extension_Scripts.ts4script and UI_Cheats_Extension.package files and drop them in your mods folder.
Repeat steps 3 - 6 for all mods that have been reported broken.
Open your game. Most updates will disable Mods/CC. We need to turn these back on.
Go to the game options > other.
Enable Custom Content and Mods and Script Mods Allowed.
Apply changes. DO NOT SAVE!!! The change to turn on mods does not occur until the game has reset, so if you save your game, it is basically saving it without mods or cc and your sims will be bald/naked and you will have to manually reapply all of it.
Restart the game and you should see the Mods/CC list prompt appear.
Once you've confirmed your mods are working again in-game, continue the process to update all your necessary mods.