Setting up a new server? Adding a new user? Installing a new package? Running a new service?
Don’t do it, write it.
It doesn’t really matter how or where you write it. Write a new Fabric task, update a playbook, update a Puppet module, or write a new one. Whatever you have to automate tasks, even if it’s a shell script.
Then run it.
Then the next time you have to do it, run it again.