A few weeks ago I bought this top in Primark. It's hard to tell from the photos, but the main body of it has delicate pleats. I loved the ruffle around the neckline and arm holes. I dithered over it for a minute or two, not sure if it would fit (I was in Primark after all), but in the end I just decided to get it.
When I tried it on at home the fit wasn't great. The sleeve holes were a smidge too tight, the top fitted, but seemed to g-r-o-w. You can't imagine it by looking at it, you just have to believe me. This great swathe of fabric just ballooned. I looked and felt massive in it. I considered a few options. Using a belt around the middle to hold it in place, but that didn't work. The fabric moved about, slipped up and spewed over the top. Ribbon made me look like a sack of spuds, and the other idea I had of stitching down each pleat just seemed ridiculous and like too much hard work.
But I kept it,and decided I could make use of the ruffle.
So when I bought a new, plain black cardi, an idea pinged in my head. I carefully cut the ruffle from the neckline (just below the seam, so it didn't unravel and need stitching. I'm lazy like that!).
I pinned the ruffle around the neckline of the cardi. 
Then I simply stitched it in place. When I do anything like this, I use a stitch that's pretty much nothing more than a tacking stitch. It doesn't need to be super strong, just strong enough to hold it in place and withstand washing. 
I tried it on to see how it looked ... 
.. but I wasn't sure that I was happy with it! I liked how it looked, but I felt it was a bit fussy. I usually have my hair down, to see the frill my hair needed to be tied up. So about ten minutes after sewing the frill on, it was snipped off again and the cardi back to being plain. I am much happier with it this way.
The reason I sew embellishments on to new clothes lightly is for exactly this reason. If I change my mind I want to be able to alter it quickly and easily. The only exception to this was when I added ribbon and beads to my [customised cardi]. That was a spare cardigan that I wasn't bothered about messing up, so used the sewing machine to attach the ribbon. When something is new and very much wanted I'm more cautious.It's also to show that if you buy something that turns out to be a mistake and can't be bothered to return it, you can use it for something else.
The ruffle isn't going to go to waste. Oh no, I'm going to attach that to the neckline of one of my plain black vest tops and wear it underneath the cardi.
black cardigan from [Woolovers]