Why do bad things happen to us?

Why does God allow suffering?
I think there's a clue in one little word in John chapter 11: the story of the raising of Lazarus to life again.

When Jesus hears that Lazarus is sick, he says:

 "This sickness will not end in death but is for the glory of God, so that the Son of God may be glorified through it." (John 11:4 Holman Christian Standard Bible)

Then we read:

 Now Jesus loved Martha, her sister, and Lazarus. *So* when He heard that he was sick, He stayed two more days in the place where He was. Then after that, He said to the disciples, "Let's go to Judea again."  (verses 5-7)

Some translations don't have "so", but I think it makes sense of the story.  Because Jesus loved Martha, Mary and Lazarus, he wanted them to see for themselves that he is the Son of God, who brings the dead back to life. This could only happen if he waited till Lazarus was dead before he got to Bethany.
And when that happened, he was able to assure them with the magnificent words:

"I am the resurrection and the life. The one who believes in Me, even if he dies, will live.  Everyone who lives and believes in Me will never die- (John 11:25-26 HCSB)