If God is loving, caring, and powerful, why must humans go through pain and suffering?

Remember that we live in a post-fallen world, and sin has altered everything. Because we were created with free will rather than as robots, many of our decisions are the consequence of our own poor judgment. And, even if we follow the Lord with humility and sincerity, if things don't go as planned, God's grace is still available to help us overcome the trials because Jesus Christ overcame the world.

I have said these things to you, that in me you may have peace. In the world you will have tribulation. But take heart; I have overcome the world.” - John 16:33

But he said to me, “My grace is sufficient for you, for my power is made perfect in weakness.” Therefore I will boast all the more gladly of my weaknesses, so that the power of Christ may rest upon me.” - 2 Corinthians 12:9