When I started I was very matchy-matchy. I tried to get the EXACT shade that was in the focus fabric. Even if it was a 1/8 inch flower than couldn't be seen from three feet away.
Then I read Jinny Beyer's book (sorry, don't remember the name of it) where she would match the colors in the focus fabric and then find "bridging" fabrics that would shade from one color to the next in the focus fabric.
She would use those colors and NOT use the exact matches. The quilts using these colors were so much livelier than the ones using the exact matches.
It's important to think of contrast, also. Do you want high-contrast or not? That's almost as important as color.
Also, stand several feet away from the fabrics. They look different from 10-12 feet away than right under one's nose.
It's also okay to change one's mind about a fabric choice. (Well, yes, one is kind of stuck with it after the item is made - but anytime before it's quilted will work)