This issue should be analyzed with a broad mind. Because if you want to find an
answer to this question you should have to break your ordinary belief.
If you are thinking psychologically your answer might be the following.
Up and Downs are common in everybodies life, it can be happen either
to good people or to bad people.

Good people means the peoples they having good qualities and manners .
But nobody can describe what are the good qualities and bad ones.
If one manner is supposed as a very good manner in your place that can be
very bad in other place or places. So nobody can describe what are the good
ones and the bad ones. So that they should Confuse who is good and who is bad.

According to the religious or spiritual theory the God id testing
the peoples; that means testing their devotion, testing the mode of character,
testing their abilities etc. these tests should be for finding some of the
best peoples among a group of good peoples.

Whatever the reason the Universal truth is, every body have to go
through some toughest situations at least once his life. because good and bad
is just like the two sides of a coin; and anything happens to good peoples
they should survive if they are really good.