Our sectional couch came with three matching pillows with piping around the edges. That was over 7 years ago. The corners were fraying and the piping was starting to show, so one by one, I resewed them.
Starting last March, I took each pillows apart, one at a time, using a seam ripper to remove the thread. Then the fabric was washed, dried, and ironed. The hardest part was threading the sewing machine but after a few false starts, I did fine. I sewed three seams with the good side facing in, turned it inside out, and then stuffed the pillow in. For the fourth seam, I folded the two edges in and then sewed through the four layers to close it... all using my sewing machine. I could have hand sewed the fourth side to make it look nicer but I'm fine with the way it turned out. (A zipper would have been nice but totally outside the realm of what I'm comfortable doing by myself.)
There's still one left to do but my Mom will be here this weekend so I can get her to sew it for me - with a zipper. The couch is gone but we still have the pillows! :)