When trials and suffering come our way our first inclination can be to complain, and the second to pray and ask God to remove it. But it is through the trial that God wants to deepen our faith and produce holiness.

It is not for us to second guess God by asking “why?”, but instead for us to evaluate our reaction and learn more about our trust and confidence in a Sovereign God who works for the good of those he has called according to his purpose.

Romans 8:28
And we know that for those who love God all things work together for good, for those who are called according to his purpose.

Regarding why God appoints suffering for His servants, John Piper says :

Hebrews 12 tells us that God disciplines his children through suffering. His aim is deeper faith and deeper holiness. He disciplines us for our good, that we may share his holiness.

The writer to the Hebrews, referring to earthly fathers, says in chapter 12 verse 10:
For they disciplined us for a short time as it seemed best to them, but he disciplines us for our good, that we may share his holiness.

So when the trial comes, as it surely will, thank God for the opportunity to glorify him by our trusting in his sovereign will for our lives and using the situation to grow in our faith and in our holiness all for His ultimate glory.