As my first dev job, I took over role of solo programmer maintaining all kinds of custom-made software used by local ISP. It was about 10 years ago.

My first question was where can I find test environment and repo. Apparently there was none and I should learn and develop on production.
My sin was to quickly give up on setting up both test and repo.

My second sin was to continue using the same copy&paste PHTML with register_globals enabled, building over it without attempting to refactor it with templates. I did not use globals in any new code at least.

And I suppose my third sin was that I was playing games when I was done with my tasks. I could have used that time to refactor a bit.

But I think in the end I was absolved from them since I was the only one suffering from this. I stayed with company until it got sold and helped migrate data over (along with myself).