I did not properly recognize my mother’s love to me and proved myself ungrateful. Before I could make amends, she left her body and now I’m feeling much guilt. What can I do to correct my mistake now?
I understand how you feel. I don’t know if this will comfort you but many, if not most, thoughtful people have deep regrets about some of the ways they treated their parents. I know I do.
Your consolation, and it is a genuine consolation, must be that despite any regrettable behavior on your part, you did give your mother the greatest blessing in the form of Krishna consciousness. Even if her complaints about certain things kept her from appreciating Krishna more, the fact is that you did engage her in many ways in Krishna consciousness, to her eternal benefit.
The best thing you can do now is to pray sincerely to Krishna to give her wonderful opportunities to serve Him. I’m sure Krishna will hear your prayers. In fact, your regrets are also Krishna’s arrangement to induce you to pray on your mother’s behalf. That will benefit you and her.
Lamentation is like everything else: healthy in the right amount. Not enough makes one shameless, and too much hinders one’s progress in Krishna consciousness. So cleanse your heart by lamentation, but also remain positive and remember that Krishna has given you the power to render the highest benefit to your mother by your sincere prayers. Also as you advance in Krishna consciousness, she will also reap the benefit.