Building things that don't break is a philosophy that people tend to carry through any field where they build upon their own work. It stands to reason that very few people set out to build things that will break if they intend to use them themselves, so why am I even discussing this topic? The reason that this topic merits discussion is that it's so easy and as a result, common to build things that do break.
As a webmaster, you'll have the need for a variety tools. You may use some tools to analyze your logs, others to manage your content and perhaps a few other scripts to get user feedback or subscribe to a mailing list. This set of tools described here outlines a very basic toolkit that most webmasters have.
What you need in order to use your time effectively, is for the tools to work without any required intervention and without unexpected failures. If you can get your tools to work in this manner, you've got some basic building blocks to build upon.
Having solid, reliable building blocks is extremely important. If you have these you can move forward in small increments, making minor improvements or additions to your tools. Most webmasters work independently and as a result have limited time to develop custom tools. This means that working in small increments will likely be the only strategy you'll be able to employ since taking on large development projects will mean neglecting your site for a significant amount of time.