Important rules to follow...
When handling magnets, you need to be careful not to weaken them or demagnetize them.
When storing bar magnets, you need to place them together north pole to south pole, as not to weaken them. Think about it. When magnets are placed with like poles near each other, they try to push away; keep it that way for a while, and you'll come back to a weak or non-working magnet.
In order to not demagnetize a magnet, you can't drop it, because when you drop the magnet, the atoms may get scrambled and won't be magnetic anymore. You also can't expose a magnet to extreme heat, as that will also demagnetize it.