I love being in the quilt shops to buy fabric. I bet you just put too much presure on yourself. Pick out one fabric you love, then just add to it but matching the colors in the fabric you love and don't be afraid to be daring and add a "odd man out" fabric. For me the problem is not always finding the fabric, but it is the cost of the fabric. I have had to substitute a less expensive fabric for a fabric I loved because it was $11.00 a yard and that is out of my budget. That is the frustrating part for me and for those that do not have that problem, bless you.
Just go with what makes you happy and it will come together. It ALWAYS has for me. Happy hunting!