It’s different for everyone, and everyone has different challenges at different stages of their training.
In my 18 years of training, here’s what I’ve seen arethe top obstacles:
1) Too many techniques to learn. BJJ has more techniques than any other martial art, and the library of techniques is growing all the time. Students can get easily overwhelmed when they are trying to figure out what to learn. And they can get frustrated when they are trying to learn too many techniques.
2) Injuries. This can happen at any stage of training, but can be more of an issue the older you get. Students may have to take time off from rolling, which can be really frustrating, but there are many things you can do to reduce your chances of getting hurt. And when injured, you do not have to completely stop training.
3) Slow Progression. Jiu-Jitsu is one of the toughest martial arts because you are trying to submit someone who often knows the technique you are trying to do to them, knows the counter, is bigger than you, is in better shape than you, and is more athletic than you.
4) BJJ is tough on the ego. Jiu-Jitsu is different than other martial arts. Most matches end with one person tapping. It’s very final. If you’re doing stand up sparring, and not doing full contact, at the end of the match you’re not 100% sure what wold have happened. You landed some strikes, you got hit several times, but you’re not sure how the fight would have worked out if you were going 100%. When you rolling and get put in a submission, it doesn’t matter if the person who caught you in a submission is lower rank than you smaller, or whatever… you have to tap, otherwise you are going to pass out or something is going to break.