Well... I got out of bed today!
Second answer, finishing a project is challenging enough!!
(And then my vision issues are a challenge. I feel in many ways that my best quilting is behind me, but that I still have years of great projects I can do. I'm just not going to be doing a lot of curvy points or a bunch of other stuff.)
Third (the long) answer, a lot of what I do in my quilting is a challenge of some sort.
From finding/collecting the fabrics to using them. As a thrift shopper, it was also a recreational activity, but I had to be open to what I got or that sometimes there was nothing good to get. But there is a definite zing! when you find a good score. I said recently in another thread that I think with a sufficient budget I can go into a fabric store and come out with a pretty good project to be. But I actually really enjoy making my various fabrics play nice together, for me it is part of what quilting is all about.
Sometimes the fabrics confound me and force me to go out of my comfort zone. Again, with thrift store shopping and a big bag of fabric you can afford to take risks that you just don't want to take with full priced fabric. Last few years I've been trying to embrace large prints when I really would rather work with more traditional calicos. Or at least my sharp vision self liked working with them. I'm finding things I can do, I love quilts that are "simple, effective, and suitable for large scale fabrics" even if the sewing isn't such a challenge, putting them together with thrift fabric is.
Recently we had a thread on Lemoyne Star. My "8-pointed" star was made not as much as a challenge but because I felt I needed some work on those set in seams. Not that I was really avoiding them but I hadn't done any lately.