Ok, this is probably going to sound like a dumb question, but - say you've been collecting fabric and have a stack of 1 yd here and 2 yds there, a few FQ's here - and then you find a pattern and think that these fabrics would be fun to use. How in the world do you know if you have enough of which one to use?? Do some patterns tell you to use so much of a light fabric and so much of a dark? Or do you just have to measure and figure?