Don't Install iOS 13.3 If You Haven't Prepared
If you haven't prepared for the move to iOS 13.3 you'll want to hold off until you've had time to prepare yourself and your device for the move.
It's impossible to predict how your iPhone will handle the move from iOS 12 to iOS 13 or iOS 13.2.3/iOS 13.2.2/iOS 13.2/iOS 13.1.3/iOS 13.1.2/iOS 13.1.1/iOS 13.1/iOS 13.0 to iOS 13.3 and that's precisely why we recommend spending some time preparing for the move.
If you don't know where to start we've put together a guide that will walk you through the pre-installation process we use before we install new iOS firmware on our phones.
If you don't have a ton of time to devote to the pre-installation process, you'll want to at least make sure your data is completely backed.
Data loss issues are rare, but if you store sensitive data on your phone, you'll want to make sure it's safe and sound before moving to iOS 13.3.