People riding over our heads

Since God has all power and is at the same time merciful, does it not mean that we should be free of trouble? Far from that. God does not promise a trouble-free life. In fact the word of God prepares the believers for difficult times, e.g. in the Psalms in the prayer “you let people ride over our heads, we go through fire and through water, yet you will bring us out into a safe place”.