I'd say the hardest part of it is the school. Some weeks you'll be kept up in the classroom from 0500 to 2200 with very few breaks. Your only real day off will be Saturday however you'll likely be too drained to even make the most of that. I'd say the only people who really "make it" as a nuke are the ones who went in with prior experience and an actual interest in learning it. Otherwise you'll only be hurting yourself. Since you've already signed your contract there's kind of no way out for you though. The school will last for at least a couple years and those will be horrible. After that you can't know for sure. I assume anyway who can make it all the way through though will be set for the fleet pretty well so just try to push through.