Nothing "bad" happens to a Christian without some good reason. "All things come of God" (2 Corinthians 5:18), and "all things work together for good to those who love God" (Romans 8:28). Don't worry about the times of testing and weakness, thinking that you must have done something terribly wrong, so God must be finished with you. What you feel is God's tender hand upon you, making you into the person He knows you can be. As hard as it is, these breakings and remakings are inevitable. He must make you weak in yourself so you will depend on His strength. He must make you humble. He must make you desperate for Him and His help.

You're in His hands and He will perfect that which concerns you (Psalm 138:8). So don't be angry or bitter at God for these testings. They are only for a time. You will rejoice and be grateful when you look back and see how this was necessary for Him to accomplish His good purpose.

Things don't just happen to children of God,
They're part of a wonderful plan.
The troubles, reverses, the sorrows, the rod
Are strokes of the Great Sculptor's hand.
—Alice Reynolds Flower (1890-1991), "It Didn't Just Happen"