When you try to breakdown an item, you spend Stamina. There is chance of failure that depends on breakdown difficulty (indicated for the selected recipe and taking in consideration all bonuses and penalties of the villager). The more damage the item has sustained, the harder and more expensive (in Stamina) is the breakdown action. There is an additional penalty if the item is completely broken (its Durability is 0).
Upon successful breakdown, all items components are received.
Upon unsuccessful breakdown, some of the components are destroyed.
See the tips section in the Workshop.