Let's forget for a moment about "I", and "wanting". Here are some:
- Minimise or eliminate "suffering"
- Minimise attachment, and craving, associated with suffering
- Minimise defilements
- Minimise fetters
Learn to practice the noble eightfold path.
Practice good deeds (and speech), and generosity, which are for example "a support for the mind".
I think that, when a monk is dying, another monk may be advised to remind him of his "attainments" -- perhaps it's such "attainments", and "good deeds", that are not (or that are less) impermanent.
As for "I can't even desire Nirvana , because I never get it" -- that seems like a contradiction, you know.
Imagine "I" is like a drop of water, and "Nibbana" is like an ocean. Then "I desire Nibbana" or "I can't desire Nibbana" is like saying, "I wish this drop of water would be as big as the ocean, as permanent as the ocean, but still be the same individual drop of water."
Then people around you are like, "Dude! Let it go! Put the drop in the ocean, already!" (or, depending on the school of Buddhism, maybe, "That drop of water is already like the ocean").
I think a reason why Buddhism teaches anatta is because it's the characteristics of "I" that are associated with suffering -- craving to have things is associated with suffering; seeing and being attached to (and wanting to be attached to) an impermanent "self" that's going to die is associated with suffering; and so on.
One advice, which I remember from long ago, is to treat your sense of self (or your body) like a wound -- you take care of it, you try to treat it so as to minimize suffering, but you don't love it, you don't become attached to it. And you don't say "I can't want to be healthy because then this wound (my sense of self) would disappear."
Also there's some middle way, for example this sutta or this sutta imply that some wanting is "right".