How do you reach Nirvana when you are craving Nirvana?

They say once you reach Nirvana you remove craving. However, don't we need to crave the state of Nirvana in order to reach it? Doesn't that contradict everything an enlightened person who reached Nirvana stands for? Because in order to continue this state, meditation and other things need to be constantly practiced which is a sort of craving in itself.