First, take a deep beath. One of the hallmark signs of a good critical care nurse is that they are too hard on themselves.
If you had no unansered questions, I'd suggest that you move on out of ICU
. I still have lots and I've been in ICU/CCU for over 12 years.
Second, you should not be caring for unstable patients at an entry level anyway, so don't worry. My experience has been that if we put an orientee, even buddied with an unstable patient, they tend not to learn a whole lot and the experience is overwhelming.
Our orientation is six weeks of mixed calssroom and clinicla followed by two weeks of buddied shifts. That seems to be enough for most folks, although most feel that they could benefit from more, objectively they do just great!
Talk to the educator on your unit about extra reading materials to make you fell more prepared, but expect to feel nervous for at least a year. We are actually paring back some of the information that is in our course, because we think that a lot of information is purged after the final because there is do much.
hope this helps,