Invest in very good testing, especially higher level integration / system testing.
Invest in a good dev/staging setup for your production environment, and also try to make rollouts and rollbacks automated and as painless as possible.
There will always be the need to change stuff, so get the pieces in place to make changes easier code, easier to test, easier to deploy, and easier to back the fuck up when you inevitably cause something to burn.
Invest in very good testing, especially higher level integration / system testing.
Invest in a good dev/staging setup for your production environment, and also try to make rollouts and rollbacks automated and as painless as possible.
There will always be the need to change stuff, so get the pieces in place to make changes easier code, easier to test, easier to deploy, and easier to back the fuck up when you inevitably cause something to burn.