Why didn't I follow the checklist!?!

Today I upgraded our Subversion server to 1.6.5. It was a nightmare and all because I tried to do it from memory. It seemed simple, just uninstall and install a few services and then I would be away laughing. However I was shown why pride comes before a fall. All was going well till Apache wouldn't start. After pushing and pulling at the configuration and reading the error logs, it turned out I should have installed mod_python. All shiny, but why isn't Trac working! Many hours later, oh yes I should reinstall the python bindings to Subversion. Look at that now it works. Later checking the wiki (to make sure it still works) I read the article I wrote on how to upgrade subversion. There in black and white was the steps as I should have taken them. Including the missing mod_python and python bindings. Why didn't I just follow my own checklist.