Not so much a paradigm, but learning TDD from the engineers at Pivotal Labs really changed the way I approach problems. I spent a few weeks constantly pairing

Not so much a paradigm, but learning TDD from the engineers at Pivotal Labs really changed the way I approach problems. I spent a few weeks constantly pairing and doing TDD with them, and while I don't think I could pair forever (maybe 2 days/week), I was amazed at how TDD could shift my approach to a problem. These days I'll still use it, even on personal projects (usually only integration tests), as a great way to reduce unnecessary complexity and increase my confidence in my own code.