Some game changers for me off the top of my head: * Automated regression testing and build/deploy pipeline. The machine will do things quickly and repeatedly e

Some game changers for me off the top of my head: * Automated regression testing and build/deploy pipeline. The machine will do things quickly and repeatedly exactly the same way, given the same input conditions/data. * TDD. Create tests based on requirements, get one thing working at a time, and refactor with a safety net. * Mixing FP style and OO style programming to get the best of both worlds. * Understanding type systems, and how to use types to catch/prevent errors and create meaningful abstractions. * Good code organization, both in physical on-disk structure and in terms of coupling & cohesion. * Validate all incoming data and fail fast with good error messaging.