From the time you start learning how to code until having a job(freelance, part-time, full-time), what concepts, techniques have you learned that help you from your entire career as a programmer ?

MINE:
OOP and Design Patterns
For me I learned Object Oriented Programming by applying Design Patterns which also helps me to properly understand abstraction and utilizing interface.

Single Responsibility
I believe it is the most common practice that every programmer should know.

TDD specially UNIT TEST
Time consuming but worth it, it helps you to refactor functions easily without worrying about having wrong implementation cause of refactoring. Writing test is fun :)

Pure Functions
Allows you to test your functions easily and compose your functions.

Monads
Composing functions with same shape(data type) of inputs and output. It helps you with problems that requires chains of transformation of the data.

Currently Learning:

• Domain Driven Design - (DDD)
• Low Level Design - (LLD)

My thoughts ?
I prefer learning techniques and concepts which can be applied in any programming languages because it helps me to write quality code.

Following the concept should be a habit because sometimes we procrastinate on refactoring making our code better, break the habit on (as long as it works then we settle) we should not settle we should improve them as long as it can be improved.

How about you guys, I want to know yours as well please share on the comments :)