The believers are purified by hardships and tests to remove their errors and raise their degrees in Paradise. The Hadeeth says: More tests come with more faith كلما زيد في ايمانه زيد في بلائه
More hardships and tests make the believer more remembering Allah and seeking His help and avoid the believer the feeling of pride or arrogance.
There are many Hadeeths that the the believer who struggles in this life for noble cause, will be more rewarded in the hereafter. We read in Quran: Those who face the hardships with patience (Sabr) for the sake of Allah will have countless reward (Sura 39, verse 10).
We also have Hadeeths that the status of Sabr ( patience) from Faith is like the status of the head from the body.