I'm fortunate to have the perspective of having worked with adults and peds in EDs and the units.
Life is unpredictable, it isn't fair, and not everyone gets dealt a good hand.
I've had plenty of kids with poor outcomes from heart disease, the flu, and just about every other thing possible.
It exists in adults too. It exists in the EDs, adult ICUs, NICUs, floors, and so on.
I think that in order to survive critical care you have to come to terms that a lot of patients are going to have poor outcomes, and be able to not take it home. We are able to recover many more patients, and give lifetimes back to so many of our kids and their families.
Over the years I've worked with a lot of nurses who don't ever really handle the stress well, and ended up leaving the units or EDs. It isn't natural to see death and suffering like we do everyday, and they found that another care environment ended up being much better for them. If you do choose to leave the PICU don't think of it as a failure or weakness.