Many people have the idea that bad karma can be reduced or removed through meditation, worship, samskara, or sacrifice. How can we really burn all our bad karma?
The Vedic scriptures describe that devotional service to the Lord destroys the results of previous sins, in other words, bad karma. The effectiveness of the process depends on its purity. For example, pure chanting of the holy names of the Lord destroys all sinful reactions. But the chanting is usually not pure in the beginning. When one begins the practice of devotional service, it is said to be like unplugging a fan. The fan will still turn for some time. So in the stage of devotional practice, the reactions will continue, but as we become more and more purified by devotional service, eventually we become free of all reactions and enjoy the bliss of full spiritual life. And even in the stage of practice, Lord Krishna adjusts the karma so that His aspiring devotees get just what they need to progress steadily toward Him.
But one precaution is very important and that is committing sinful activities on the strength of the holy name because this is an offense to Holy name. If one continues to perform sinful activities thinking that he will be freed of sins by chanting Hare Krishna then it is an offense to the Holy name. So one should be very careful in this regard that whatever sins had been committed in the past we do not have any control over them but now onward when we start taking the shelter of Holy name we should not commit further sins.