Yes for some people riding a unicycle is very difficult and sometimes not even possible.
I tried myself for years to try to ride a unicycle and never could get the hang of it and finally gave up on trying to ride a unicycle.
I barely got a few feet on the unicycle and then would fall and I never could get the hang of it.
And even a friend who could ride a unicycle with ease after years of practice tried to teach me and help me to ride a unicycle and I still could not ride the unicycle.
Then again some people can easily ride a unicycle so if you cannot ride a unicycle you certainly are not the only one.
I would love to be able to ride a unicycle but I can't do so but my brother can ride a unicycle and he was able to ride the unicycle his first try.
But for some people it takes longer and for some people they can not ride a unicycle at all.