- "The positive aspect of a hazel wand more than makes up for such minor discomforts, however, for it is capable of outstanding magic in the hands of the skilful, and is so devoted to its owner that it often 'wilts' (which is to say, it expels all its magic and refuses to perform, often necessitating the extraction of the core and its insertion into another casing, if the wand is still required) at the end of its master's life (if the core is unicorn hair, however, there is no hope; the wand will almost certainly have 'died')."
- —Garrick Ollivander's notes on wandlore.[src]
A wand can wilt following some kind of stress in the relationship between the owner and the wand: hazel wands are prone to wilt following the death of their owner (when coupled with a unicorn hair core, it makes the death of the wand a near-certainty); sycamore wands will wilt if allowed to become "bored" (wilting is accompanied, in this case, by the wand bursting into flame of its own volition); other wands can "die of shame", by not conforming to the use their master is giving them.
If a wand is still required after wilting, the extraction of its core and its insertion into another casing can be attempted. However, in the case that the core is of unicorn hair, this attempt might be fruitless, as the core itself may die (unicorn hair is particularly prone to melancholy if seriously mishandled).
It should be noted, however, that not all wands are prone to wilting.