Stickwithitness is a delightful, if somewhat uncommon, neologism that fits this description.
Two examples from the wild:
It’s hard keeping a blog. Isn’t it?
Buying a Los Angeles Home Requires Stickwithitness
Note that the phrase “stick with it” apparently was not used, at least per published books, until 1964.
Compared with “Stick with it,” the exhortation “Hang in there” has similar, but distinct meaning. The latter is also more popular. However, note that Google only has 4 results, as of today, for the non-word “hanginthereness.” (Two words are actually individually quoted, in acknowledgement of their non-existence.) I would postulate that this lack of parallelism with “stick with it” is because “hanging in there” requires little action — merely the maintenance of hope; however, sticking with it requires continue action in the face of discouragement.