A few things I like to do for uphilling rough terrain:
1.) Strength(endurance) & Coordination: If you have plenty of strength at the base, but you start getting tired at a certain distance? Of course you will fall because coordination is gone with strength. Unless, it get’s flatter(easier) at the top, but I am assuming a constant angle. Then you might consider just doing repetitions and make a note of your rest time and the location where you fail. Eventually, you will get stronger.
2.) Stall control. From my experience riding up hills on my 24" muni this is what I tend to do. Take it one step at a time, and I am pretty much “stalling” between each pedal. Crouch forward and pinch your thighs together for saddle control. Also, allow the unicycle to wobble side/side a little bit for stability. It works. (You ever watch George Peck unicycling over rocks?) Keep both hands off the saddle and “free” to help with balance. To stop/go successfully you must not only be able to stall, but be able to throw your weight and rock the unicycle forward/back with control/speed/precision. So, a great exercise to develop your ability to ride slow and stall without falling is unicycling on grass with hidden bumps and gopher holes. It’s all about keeping your legs tight/ready to deliver precise stop/go power and duration when needed. Can be a very exhausting workout, but falling down on grass is safe. As I get better, I attempt a few raised tree roots.
3.) Do not rely on speed or momentum. Unless, you are on a very smooth surface. If you are going to encounter rocks and bumps at the same time as steep uphill, you need to “work” over every bump or drop with one pedal at a time. This is true off-roading, but twice as difficult because you are not down hilling with gravity.
Anyways, have fun with your hatchet. Keep on.