For me stash just happens. I only buy for specific projects, and buy the yardage suggested in the pattern. Some patterns have you buy way more than you need. I have several totes full of different size cuts of fabric that I don't know how to use. I keep looking for a scrappy pattern that I like to try to use it, but just haven't found one.
I think the biggest problem is I am so anal and not an artistic cell in my body.

I agree with Ghostrider! It gives me a warm, fuzzy feeling when I look at my stash and think that I'll have what I need for a spur of the moment project. Of course it doesn't help when I buy maybe 10 yards total to make one lap quilt because I love the fabrics together.

A large stash can be both liberating and paralyzing. I have accumulated far more fabric than I intended, but I do sew entirely from my stash, and pick up new fabrics when they're on sale.

Stash is both a blessing and a curse. It's wonderful to have enough fabric in your stash to complete a project without paying $13-14.00 per yard at the LQS. Still, no matter how much I have accumulated, there is always that elusive 1 yard or so that I end up buying to complete a project. Lifting large plastic, stash-containing totes sure could tone up the upper arms - or give one a hernia!

This past Spring I cut up some of my stash into 2 1/2" strips. Obviously they weren't the same length. I pretended they were from a jelly roll and made the jelly roll/ 1600 quilt. It was awesome.

I have started cutting up the odd pieces into 2.5",3", and 4" squares. Then separating those by size.

I have also cut some of them into circles to make yo-yos. Only heaven knows what I'll do with then, but they are fun to make when I feel brain dead and watch TV.

My goal this year was to use my stash and not buy fabric. I have made 3 quilts and have bought backing for one. I don't see the stash going down but it must be.

I have accumulated lots of fat quarters that I am trying to use up (and not buying more) - Now I don't buy any fat quarters unless I have an immediate need/use.
Re the yardage type of stash - I had some that I have accumulated, and some that I was given. The stuff I was given isn't all to my taste and if I don't start to use it soon I'm going to give to the guild for charity quilts. The stuff I purchased I really like (still) and I am using it up as much as I can.
I also see it as a reserve fund for when I want to quilt but don't have money for new fabric or don't want to go out to shop.

I am using up a lot of my stash making beads of courage bags, if you are in a guild in Tucson there are lots of ways you can use your stash and help others

I think some colors simply are not available all the time.
So it is nice to have them on hand, if one wants them.

I have also found that if I want to shop for - say ten browns at one time - I can hardly ever find that many I like together all at one store at the same time.

I subscribe to the "stash as pantry" school of thought. As others have mentioned, I shop almost completely from stash. It's kind of amazing how if you concentrate on the color family and not the pattern in the fabric it is much easier to design from stash.