improve your code reading skills
Do you know what's the difference between a junior developer and an experienced one? The first one's eager to show off his newly acquired coding “expertise” by writing everything himself/herself. Whereas an experienced coder would always seek to leverage already existing work. So, if you're aiming to abide by a senior developer's principles, you should strive to constantly improve your code reading skills. For if you want to write great code, you first need to be able to read other people's code, to fully understand it: how do other developers think and operate?