Here’s a quick corollary to Friday’s observation about making sure of your assumptions.
If you are writing tests for your code, and you’re tracking code coverage, you may find that coverage drops after adding those little checks and return phrases. It’s probably because you didn’t write your test for that phrase first! That bit where the check fails and you return early needs a test, too! (Otherwise how will you know that your check is checking the right thing before bailing out of your method?)