Depends on who it is coming from - like Ripose posted. If it is from someone who I respect and admire - it is very hard (I am also a ACoA) which makes it very difficult on my feelings. I have to really work at not becoming hurt or embarrased and it takes me awhile to get over it.
If it comes from someone that there is really no mutual respect - I usually say something back - invalidate what they are critisizing - or just ignore.
In general I do not take criticism well. I'd like to see what others say about it as well..