A little general, but...
I'll bite. I winged fairly recently, though, so I'll restrict myself to answering your first question and get back to you on the second...
For me, the most difficult part of my road to the 1320 (NFO designation) was OCS. It's challenging and demanding, and designed to grind you down and put the fear of God, your chain of command, and Marine Corps Drill Instructors into you (I still get a little bit of pucker whenever I see a Gunny). That being said, you or anyone else can get through it if you start off with a minimal level of competency, considerably more humility (you will struggle with some things and you'd better get used to it), and a large amount of mental toughness. OCS will either break you or put an edge on you that will carry you through API and flight school (even if that edge gets a bit dull as you wait in A-pool for eight months). From there, it's mostly a matter of doing what you're told (studying in groups really does help, even if one sometimes gets off topic) and being willing to put in the hours necessary to study and plan flights, because that's what you'll be doing later as well. Since it's not really a matter of stick-and-rudder skills for NFOs, as opposed to pilots, what it comes down to is maintaining your desire and motivation to succeed--which can be difficult at times. But many have made it through to wings, and that was certainly one of the proudest moments of my life.