What kind of doubt do you mean – doubt that magic really works? Doubt that this particular spell will really work? Doubt that you deserve what you're casting for?
Mike has posted some interesting thoughts about doubt in magical works. You can find them here and here. When I think about doubt and magical workings, I think that if doubt is entering into the picture, it’s better to not do the magical working and instead really examine your doubts and why they are coming up. When I do a practical magic working I don’t want doubt to be in the picture, and for me it isn’t. I know what I want, I understand the consequences around getting it and I’m ready to handle the reality of achieving it. Doubt is a sabotager…its that little voice that says, “You don’t deserve this.” And if you hear that voice, then you haven’t done your due diligence.
What is due diligence? It’s doing the internal work necessary to ensure that the desired result (or manifestation) is something you truly want with all of your being. It’s addressing the doubts and resolving them before you even do your magical work.
It doesn’t surprise me that some magicians experience doubt and have it sabotage their workings. I think this is due to the fact that they haven’t done that necessary level of internal work that’s needed to make sure everything is in alignment with the desired outcome. Without a process for doing dedicated internal work to address doubt and other sabotage emotions, those emotions will present themselves in your working and undermine your results. But with a dedicated process for internal work, its easy to deal directly with any doubts or other emotions and resolve them in your favor. Then do the magical working and you’ll get consistent results.
This actually applies to decisions you make in general. For example, when I decided to rebrand my one business, I had already gone in and done the internal work to deal with any doubt or fear I may have felt. Once that was cleared out of the way, I started my rebranding and pursued it wholeheartedly. I didn’t leave myself room for doubt, because it would’ve slowed me down. I knew what I wanted and I knew I could do it. The business is rebranded in terms of content and message (The visual design is still being reworked) and the previous services have been let go of.
If we look at this from a process approach what we get is assess the change you want to make. Determine if there is internal resistance (i.e. doubt). Resolve the internal resistance or make a different choice (sometimes there are good reasons not to do a magical working or life change). Do the magical working and any other actions needed to manifest the desired result. Simple, effective…and the doubt is dealt without having to continue entertaining it. There should be no room for doubt if you really want to manifest a desired result.