I do a lot of sewing, from bags, to quilts and all in between, but for me, I keyed in on an item that I have used over and over and truly loved, it is unique, a perfect size and quality that lasted through the years.
Making the same item could get boring, but I can be creative in changing the fabric which feeds the creativity gene. . . but honestly, loving the item yourself, makes it fun to make, knowing I'm passing years of pleasure to the buyer who will also love the item, sew that adds the joy to the boredom of making the same item.
Sew my advice, is to key in on an item you have made for yourself, or purchased, that you can recreate, something that you use all the time and love it, something unique you have gotten a lot of admiring comments on.