I just ran across this great quote by Edsger W.Dijkstra:
It is practically impossible to teach good programming to students that have had a prior exposure to BASIC: as potential programmers they are mentally mutilated beyond hope of regeneration. (link)
The quote made me think of moving from Subverson to Git but there are lots of other great analogies. Going from document management to web content management can also be this way. For example, document management people tend to focus on files and metadata and it is hard for them to grasp that web content can be structured so there is no need to separate the two concepts. Breaking out of old models and thought habits is difficult, I find the only way to do it is to trust the new way and be willing to let go of your instincts. It is also helpful to have a zen-master style coach bringing attention to your implicit assumptions and supporting you when you stumble.