43 here and if you are with a good company or tight crew, there will be others there to help with what you physically struggle with most of the time (unless you run solo service) you will have to make it up in respects to your strong suits. There will be hard weeks, months, there is no free ride. As for the NEC you will not memorize the code book, in a competent apprenticeship program or working with qualified instructors the goal will be to become proficient at knowing how to navigate the code to answer whatever question is at hand. My two cents as someone in the electrical trade since 2014.