Humans have a bad history of getting things right without the guardrails. We know how to do it, but there often is one code path we didn't think about correctly

Humans have a bad history of getting things right without the guardrails. We know how to do it, but there often is one code path we didn't think about correctly - we may get it right 99.99% of the time, but that leaves a lot of mistakes in the code. I want guard rails to ensure that I got everything right, not just 99.99% of the cases right.