I've noticed that the majority of books on magic and indeed even the online writing I come across is mysteriously devoid of the mistakes practitioners make when practicing magic. I'll admit I find this to be puzzling and less than useful for purposes of magical work, because in only presenting the successes a person has had with magic, what is missed out on is the process of trial and error, the refinement of technique and the recognition of the opportunity to learn. In both my books and blog articles, I share my mistakes in magical work because I find it useful to keep a record of what hasn't worked, as much for myself, as for the reader. A record of my mistakes helps me keep track of what hasn't worked, so that I can work on such processes further. It helps the reader see the process of evolution that a given technique undergoes as well see where mistakes were made. It also teaches the reader that mistakes are a natural part of the magical process and should be embraced as opportunities for learning.
No matter how skilled you are, inevitably you'll make a mistake. It's important to recognize the mistake and acknowledge it. This may be hard to do, especially if it brings up hard questions for you such as wondering if magic really works, but asking those questions are important and when you hit that moment of doubt, it actually is an indicator that your approach to magic is starting to deepen. A mistake challenges us to be honest with ourselves about our magical work and its relative meanings in our lives. If we only ever have success we don't really know what we can be capable of, because that success limits us from discovering what we really need to improve on.
When I make a mistake in my magical work I use the mistake to look at my magical process and determine what actually went wrong. Sometimes what went wrong was a failure on my part to account for an internal value or belief that conflicted with the desired result. Self sabotage occurs as a result, when such a conflict occurs, because if some part of you is against what you are trying to do, then that part will find a way to sabotage your work. Sometimes what went wrong is a failure to account for an external variable that effected the magical working. We won't always be able to account for every variable that could effect the working, and so if such a variable enters into the equation its worth noting what it is and planning for it the next time you do a magical working. Sometimes the entire process just doesn't work and you need to look at what you are doing and figure out how you aren't utilizing the principles of magic effectively. It may be that you haven't adequately understood what you were trying to do or how the magic should work and that lack of understanding can create mistakes because you're not fully understanding what you are trying to do.
Whatever the reason for the mistake, embrace the mistake for the opportunity it is. It is an opportunity to learn about your magical work, to learn about your process of magic and how you conceptually and practically connect to the world around you. If you can embrace your mistake in that way, you will learn a lot about magic and yourself and become a better person and magician for doing so.