I prefer to speak about "confidence" but I agree with this point quite a bit, if I am making changes and am not certain if my changes will cause breakages I'll manually test things and codify those manual tests are integration/unit tests so that I never need to write them again. Then in the future I can modify code in the same neighborhood with confidence that any breakages I'd cause would be caught by my tests - add in a willingness to liberally add regression tests for any errors that do make it through and I think this approach can really decrease the labour required to make changes, but it does front-load more cost.