I have done a lot of substitute teaching. One of the things about being a sub is that you are only sort of a teacher. Just sort of. You can assign work, and take up papers, you can help people with their assignments and answer questions (if you are familiar enough with the subject). But day-to-day substitutes never really evaluate students, one of the primary tasks of every teacher. We can pass on that a student didn't seem to understand a particular topic, but we rarely grade papers or homework. We don't create tests designed measure a student's comprehension of what has been taught in class. We can give instruction, but it is always very limited instruction because we don't know the broader context in which the teacher has been instructing the students over the previous weeks. Substitutes can help but they can't really replace the teacher.
Sometimes, in our daily walks, though, we are all too ready to replace one of our best teachers, the Word of God (with guidance from the Holy Spirit) with a substitute. We take time to listen to good preachers on the radio or on TV because we can catch them when it is convenient. We read short devotionals (hey, nothing wrong with those!). We listen to Christian music and go to concerts. We read books on Christian living by famous pastors and authors. But, on their own, each of those things amounts to nothing more than, maybe, a good substitute teacher. Their power and influence are extremely limited when compared to the power of the Word of God. "For the word of God is living and active. Sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart" (Hebrews 4:12, NIV).
All of these other resources can be excellent aids in our daily instruction and communion with God, but they are incomplete and weak on their own. Hopefully, each of these aids take their clues from God's Word (I know I try to center each devotional there) but they are all subject to their incredibly corruptible and fickle human authors, and even when they are not, none of them have the power to "judge the thoughts and attitudes of the heart" as effectively or as powerfully as the undiluted Word of God when the power of the Holy Spirit works in our hearts.
I am flattered you have taken the time to read this and I hope that this devotional aids you in your walk. But if you have to choose between making time for this or any other aid and the pure, unpolluted power of God's Word, I hope you choose the latter. Nothing else can penetrate our hearts as deeply or as powerfully. Keep around the aids that you use (like Stickler's Musings) but make sure they don't become a substitute for the real thing.