Thank you for your letter; I too hope others will learn from your unfortunate experience. Life isn't always the way we wish it were, but if others can learn from our failures and mistakes, something good will come from them.
Your mother was obviously an unhappy and troubled person, and you might have been able to help her, had you realized why she had so much inner pain. While you couldn't have done anything about it as a child, as you grew older it might have been possible, as you learned to forgive her and love her in spite of the past. The Bible tells us to "Carry each other's burdens, and in this way you will fulfill the law of Christ" (Galatians 6:2).
At the same time, don't let the past keep you in its grip. If you still harbor anger or bitterness in your heart, or if you have emotional scars because of the past, I urge you to bring them to Christ and ask Him to heal them and take it away. God loves you, and His Son came to wash away our guilt and heal our hurts. Open your heart and life to Jesus Christ today.
Even now someone reading this may be filled with anger or bitterness because of what has happened to them in the past. But these are poisons that will destroy you if you aren't careful. Instead, let Christ's forgiveness and love fill your heart today.