Some hardships are involuntary, such as abject poverty.
However other hardships are "accepted" because they are deliberately taken on, perhaps with a long-term goal in mind.
A person may have the choice of taking a modestly-paid job upon finishing basic schooling, or pursue higher education at university for several more years. Those years may be difficult if they have to support themselves during their education without the income of a full-time job, but they believe that it is worthwhile to endure that "hardship" for a few years because they have the prospect of a better career at the end of it.
So, in your sentence:
"If you really want to achieve the accomplishment like mine, you would have to accept the hardship and have experienced it for twenty years"
the writer is saying that they experienced hardships for twenty years to achieve what they did, and if anyone else wants the same achievement they must put in the same hard work and endure the same hardships. (This is quite a common attitude held by so-called "self made men" - that is individuals, often from a working-class background, whose success in business came from their own hard work. They are often portrayed as having disdain for people who want to know the "secret" of their success, as if there is a shortcut to it)
Incidentally, I have to say the sentence as written isn't great English - the phrase "achieve the accomplishment" is a bit of a tautology. It is almost the same as saying "accomplish an accomplishment" or "achieve an achievement"!
I would just say:
If you really want an achievement like mine....
Hope this helps!