If it isn't already, encrypt your private key, so that you have to type your passphrase when you connect. You can do this with:
openssl rsa -in <old key file> -out <new key file> -aes256
Once you've confirmed it works, delete the unencrypted version.
Also, Ensure that the user you're logging in as has minimal privilges over the production system. Don't log in as (or make frequent use of) root. Ask your sysadmin to set up sudo for any high-privilege commands you do want to run.
Finally, don't bother putting any custom hoops in your own way. Very quickly, you'll get so used to them, that you'll autonomically jump through them without actually doing the thinking that it was supposed to prompt. Far better to just take general care with what you're doing.
That said, as a useful visual clue, setting up the shell background or text to be a different clour can help you rememeber which system you're on.