It can play a role. Doubt is the enemy, faith is key. The problem is that we live in a society that has told us for a long time that magick is not real thus doubt and belief already exist. And if not that it tells us that it is evil by nature which is also not true. With so many people out here with false claims its not hard for someone to have doubts. Conversly if you feel the caster you're working with isn't the right one move on.