@gelman -- Was in the exact same circumstances as you 11 years ago... cum laude grad, who went straight to the ICU. Additionally, before going into nursing, I had already earned two advanced degrees / licenses in non-nursing fields, and was an older student (50s).
Loved the medical environment, and was so appreciative of the opportunity afforded me... and consequently worked my butt off learning... both on the job, and on my own time... spending nearly all my free time devoted to the study of basic and advanced topics related to ICU practice.
Long story short: the experience didn't work out. I encountered tremendous jealousy, and witnessed an unbelievable amount of immaturity on the part of co-workers, as well as a management team that was clueless / weak in handling this HR issue. I resigned after almost a year, but remained in nursing 10 years before retiring last year.
Looking back, I think it may have been better to have started out in a step-down unit, and then moved up to the ICU after a year or so.
Not knowing all the particulars of your own situation and personal factors makes it impossible to give specific advice.
Generally though, my sense is to encourage you to NOT give up or drop out of nursing at this time... clearly, one year / one position does not make for a conclusive trial. Instead, I'd suggest checking out other options within this field.
Please keep us posted.
Hope things work out.
Feel kinda like I'm looking back at myself in this post, gelman. All the best to you!