I love homemade pasta sauce - red sauce, cream sauce, cheese sauce, I enjoy them all. But, sometimes when I make homemade sauces they tend to thicken up more than I'd like. The answer - add a splash of the pasta water to the sauce. It will help thin the sauce down without watering it down; the pasta water contains some starch from the cooked pasta and, hopefully, a little salt. (You do salt your pasta water, right? It is the only chance you have to season the pasta.)
I usually add a 1/4 cup or so at a time until I reach the consistency I'm looking for.