I haven't made that many quilts but I make lots of other sewn things and I think there's a lot of crossover in thought process.
Sometimes it starts with a fabric or several. In that case I may look at designs to figure out what pattern would showcase that fabric best. Depending on time frame I may not find something I like for months. Once I do then I gather whatever coordinating fabrics and notions I need.
Other times I have an idea of a pattern and a sense of what sort of fabric I'm looking for and I may either gradually collect fabrics or I may go hunt them down. I'm starting a quilt now that began with an idea I have had for several years and two fabrics that were meant for another project that never got done. So I've added five other fabrics and now I need to do the math and get to work.
In the case of quilts or curtains, I am generally using fabric bought specifically for use in a quilt or other fairly large project. On smaller projects I am more likely to grab things out of my stash and maybe only buy one or two things to complete the project. Different kinds of challenges with each.
If you have fabrics you really like but not enough of them then you get creative with how you use them. As PP mentioned using larger or double borders. You can also use sashing between blocks. You can also break away from tradition and use larger expanses of a "background" fabric. Maybe just have your traditional piecings floating or don't do traditional piecing.
Someone just posted a beautiful
baby blanket made on a white background with circles of different fabrics - looks awesome. She used a much smaller amount of the patterned fabrics than would normally be needed to piece the size quilt she made. Looks like 5 different prints, maybe only a fat quarter of each! Hope you find that as inspirational as I did.