Nothing seems difficult at all once you've accomplished it and you're looking back. So I don't think anything I did is really that difficult, because it isn't! It's just about staying in the shit until you're out, and having the best time that you can. Pain is temporary, to beat the dead cliche.
Most importantly: nobody does it alone! Nobody, ever. There are people around you that will be willing to help you and you should do your best to make sure they succeed as well. If you really don't think you can make it through something alone, you probably should be asking someone for help. You'd be surprised how willing people are to help you succeed.
My ass is being saved by kids one minute and I'm saving their ass the next. In the field I check my buddies constantly to make sure they stay hydrated, but also that their sense of humor is intact. My buddy will do a foot check after a long day of moving in slopping wet boots to make sure I'm avoiding trench foot, but also throw a giant fucking brown recluse spider at my face an hour later to make sure I'm keeping my bearing and my sanity.
So for me, I like to keep things lighthearted and force myself to be enthusiastic, don't take shit too seriously because it's all really a game, so play it and have fun. One of my leader's reviews on me said: "Always shows enthusiasm, even when he's faking it." And if that works, then it fuckin works!