What is the biggest mistake a coder can make?

Question

This is a serious life question, in terms of career choices and more detail oriented situations.

Answer 1

to stop learning and developing his skills..

Answer 2

fixing a bug but not knowing how or why the fix worked.

Answer 3

Being overconfident.... (biggest mistake forgetting a semicolon in a huge program)

Answer 4

Quitting. There is no worse mistake than that.

Answer 5

Forgetting a semicolon

Answer 6

when coders become arrogant