There are a couple of ways to look at the need/want thing but it mostly boils down to looking at it with a positive approach or a negative one... If you start with a negative slant the whole need/want test is all about not being able to have something you want while, on the other hand, the positive approach becomes all about working through the process to sort out what you actually need.
Me, I simply try and sort out what I need and avoid thinking about stuff I might want. Working on the need first level long enough I find that most of the stuff I actually want tend to be things I need.
That said, sometimes you need a bit of outside help to get with the program but no one as yet is doing a VolkCruising class... though to be honest we are thinking about it and would love to hear from readers if they feel there is a need and if so what would you be interested in having it cover?.
In the meantime, you might want to consider a class like the Tiny Transition and Downsizing class being taught by the Comet Camper's Mariah which, while not about boats, is very much about living and thriving in small spaces like boats.