I try to avoid it, but if its something noticeable sometimes it cant be avoided. When I can, I try to kind of undo my stitches, really carefully pulling out what I did one cross at a time so I can reuse the floss. If its too hard to get it out or it more than a few rows of work, then I go to straight up frogging.
I always frog any mistake, my mother taught all of us girls to have pride in our work. If I was to leave a mistake I would see it every time I looked at the framed picture
I will frog depending on what the pattern is, how many stitches I need to rip out and how the already in place stitches around the mistake look before frogging. I do change the pattern sometimes. ;P
1. Find the mistake. If it can be fixed/worked around without frogging then dont frog.
2. If it cant be fixed or you cant find the mistake, frog.
3. If the mistake takes ripping out a huge section, but you are close to the end of the project then its worth it to fix.
4. If you are near the start of a project, sometimes ripping all of it out is the best option.
5. If you are suddenly stricken with so much grief that you cant even look at your project anymore, put it away and decide what to do another day.
Im a perfectionist and cant stand mistakes, but if its not going to affect the rest of the pattern, I wouldnt worry. But if it throws the entire thing off-kilter, Id frog