This is one of the greatest problems that troubles philosophers around the world.
Why do good people suffer?
I think the problem can be solved if we understand that it is not really a problem.
Who are we to know that suffering is “bad” ?
Who are we to know that being “happy” in this short material life is our purpose on this planet?
The real problem is not why some pious, humble, believing people suffer, but why some do not.
The safest road to hell is the gradual one – the gentle slope, soft underfoot, without sudden turnings, without milestones, without signposts.
C. S. Lewis
Are you so certain that you do not need any signposts? How “good” and philosophically beneficial is to never be sick or unhappy, in a life the meaning of which is to allow you a glipse at the eternity of nothingness one day? How “good” and philosophically “proper” is it to never have to think of death in a life which leads directly to it? How can you live without death?
Perhaps suffering is a reminder to turn to personal insight (ενόραση), as Hannah Arendt postulates, in contradiction to the pleasures we all seek in this life. Because these pleasures (e.g. a full plate of spaghetti) make us live through other things and take us away from the One which we all feel when alone. And we surely need more of that than spaghetti…
Pain makes everything more clear. Pain drives us to see into our self. And no one likes that…
Denn das Schöne ist nichts als des Schrecklichen Anfang, den wir noch grade ertragen, und wir bewunderen es so, weil es gelassen verschmäht, uns zu zerstören. Ein jeder Engel ist schrecklich.
For beauty is nothing but the beginning of terror, which we still are just able to endure, and we are so awed because it serenely disdains to annihilate us. Every angel is terrifying.  ~ Rainer Maria Rilke, Duino Elegies
Beauty is the beginning of terror. Love is the beginning of loss. Great emotions are tangled up in our own dissolution or the loss of those we cherish. Life is a vale of sorrow. But sometimes our most sublime experiences happen just at the edge of tears. 
Kierkegaard said that pain makes us drive our thought away from this world. And if pain gives true meaning to hapiness in the eternal, then he who is suffering will feel real joy for his pain. (Afsluttende uvidenskabelig Efterskrift til de philosophiske Smuler)
Pain is an inherent integral part of the cosmos. It is connected to being itself. And so God says: There are places in the man’s heart which do not yet exist. And then pain comes into the heart. So that these places can be.
Think about it: Love is leading to Pain.
Sooner or later you will be separated from the person you love.
And not too many people want to go there.
But the only way to reach Resurrection is Crucifixion…
The sin of Man when he ate from the Tree of Knowledge is that he gained a false knowledge of the existence of Evil even though such thing does not exist. With “knowledge” we forgot that all we see is an illusion. Pain wants to remind us of this Truth. And the more we resist, the more we suffer…
The misfortune of existence makes us wonder.
But wonder we should not.
Ἀρκεῖ σοι ἡ χάρις μου· ἡ γὰρ δύναμίς μου ἐν ἀσθενείᾳ τελειοῦται…