What I tend to do, after having learned from bitter experience myself, is select all using CONTROL-A, then I cut using CONTROL-X, and then paste it right back in using CONTROL-V. Why do I use cut and not copy? Well, I am paranoid, that's why. If I use cut and I don't see the text disappear, I know I mis-typed. If it does disappear, I know I've successfully copied it to the clipboard just like using the copy command CONTROL-C. If I just use the copy command then I have no visible reassurance that I have copied correctly.