I just bought what I wanted and thought I had a use for, and then didn't get around to actually sewing much of anything... hence the stash! After I decided not to be embarrassed about it, I did more recreational shopping without guilt and referred to increasing fabric collection as my 401s (S for 'stash') everyone has to save for retirement after all. Now I have a new grandson and need to shop some more since my 401s is sadly -) lacking in cute fabric, let alone cute little boy fabric. If I were to advise anyone I'd say buy basics first - use your coupons for rulers, etc and a whole roll of batting if you have space and fabric you love. Get a good sewing machine while you have money coming in that you can spare. When you do retire try to put some of that stash into everything you make - but you may have to supplement buy a trip to the fabric store.
As for the mistakes - my local senior center runs a crafts/fabric thrift store. Some of my old calicos are going to take a ride as soon as I can find them (luckily I wasn't buying during the mauve trend)
My 401s is healthy and thriving.