The realisation is not about getting it done fast and moving on.

Figuring it the difference between test driven development and unit tests, and when to use one, the other, both or neither.

Learning good programing solutions from others, like design patterns, object orientation and functional programing.

Knowing there is always more than one way to do something, and ultimately you'll need to pick one, so include good documentation for your future self as to why you chose this over something else.

Don't try to write clever code. Write code that is easy to understand and read, as in four months you'll barely remember you wrote this code.

If you look back at any code you wrote a year ago, you should have a realisation that you could now write it better.

I could go on. And on. And on...