Consider making your blocks without being too picky about fabric selection, then put them up on a design wall and remove the ones that make you less than happy. See if the removed ones work together in a different quilt. I often end up with a secondary project made up of the misfits from the first.
Another strategy I use sometimes is to make a "rule" about the included colors. For example-- only colors that could potentially be found in a high fructose corn syrup candy. Or only fabrics that would go with a pair of brown lace-up oxfords. Your rule will be highly idiosyncratic and specific to you, but it will provide a framework for you to make inclusion and exclusion decisions.