No parent is perfect; we all can look back and think of ways we could have been better parents to our children. That's why every parent needs God's grace and forgiveness, for only He can take our failures and make something good out of them. When my wife, Ruth, is asked how to be a good parent, she always replies, "On your knees."
But it's important to remember that we aren't responsible for everything that goes wrong in our children's lives. They alone are responsible for their decisions, and they alone must reap the harvest of what they have sown in life. Even good parents may have children who rebel, or who go through life making wrong decisions. Many parents have had the experience of pleading with their older children, urging them not to do something that is only going to give them trouble—and yet they refuse to listen.
If you know where you have failed as a parent, ask God to forgive you—and He will. Ask your children to forgive you also, and let them know you will always love them. Then pray for your children, and ask God to help you find ways to encourage and help them.
Most of all, make Christ the center of your life, and urge your children to do so also. Only He can heal the brokenness of our lives—and He will, as we trust Him. The Bible says, "He heals the brokenhearted and binds up their wounds" (Psalm 147:3).