I like your turn of phrase - 'fabric diet'. I'm on another group and for a year joined their no-buy challenge and was pretty successful at it but there were times when I wanted to buy something after serious consideration so I challenged myself the next year not to buy on impulse alone. Fabric diet is a perfect description for this. You don't buy on impulse, but you need to treat yourself very occasionally and with great thought when you do.
I have pretty much gone no-buy for everything except what I need to finish projects that I have started - thread, batting, border fabric etc. When I started quilting I bought lots of books on different techniques and styles, some new, some used. I found that what I used my books for was browsing for design ideas when starting a new quilt. I never actually used the patterns. I went through and only kept those that had techniques I wanted to try out in the future, lots of inspirational photos or encyclopedic style for reference.
Diana