Ensure the really important stuff (passport, wallet, phone) are on my person at all times. I have a specific jacket (lightweight Decathlon waterproof) with lots of zip up pockets. Important stuff goes in there

If I can't wear a jacket for any reason (i.e. it's bastard hot) then I have a small fanny pack (Patagonia 1L Blackhole) where all the important stuff goes, which is then worn next to my body under any shirt/top layer so it can't be gotten at easily.

Also carry a USB drive in a separate place which has PDF backups of my passport, any visa documentation, any relevant booking or travel stuff (like flight confirmations, reservations etc), and any other important documents so that I can still function if the absolute worse happens.

If I'm just out for the day, then credit cards and other bits of plastic stay in the room (in a locker or safe) and I'll just take out what I need in cash for the day (and maybe a chargeable card like Revolut just in case). Will also leave passport securely locked up where possible and just carry a photocopy in case I need to show ID anywhere. I travel with a minimum of 2x padlocks so I can always make sure I'm locking whatever needs locking with something only I have the key to.

I also carry a paper copy of credit card helplines in case I need to cancel anything ASAP, and address/contact details of local embassy.