To become a masterful sculpture you must understand the properties of the matierals you plan to work with, the right tools to use and how to maintain those tools to effectively create a more appealing finished product. Most importantly, you must have a vision of the finished product. This can be an arduous and lonely process for the artist. - to be continualy be maintaining the tools and searching for just the right materials to use while at the same time supporting them selves and simply staying alive.
Similarly, to become an effective believer in Jesus Christ, we must know the "tools" we've been provided by our hevenly Father and what our ultimate goal is. Knowing when, where and how to effectively use our "tools" when our opposition try's to resist us by distracting us and making our tools less effective hindering us from reaching or goal of making disciples of all nations. Jesus has ALREADY taken the burden of maintaining our tools from us by empowing us to tell Him what we need (through prayer).
The Armor of God is the tactical tool that help us fulfil our strategic objective of giving everyone a chance to meet Jesus.