My sister gave me some cute Christmas fabric with mittens. One red and one green. I was afraid to cut them until I was really sure she did not need them back. About a week ago, she emailed me and said that she needed a bit of the green on because she'd run short. I am so glad that I did not put that into another project.
I know what you are feeling. I ran short (sort of) on a border once. I was able to find a bit to finish. It was only short by about two inches, but I felt a bit silly.