It is, like most things Vedic, aimed at breaking the illusion and thereby speeding us more towards liberation rather than bondage. The idea that we can fix karma is foreign to me. In general, I don't like that mood. I rather like the mood of surrendering to God, and entering a life of devotional service in order to find inner peace and inner release from the bondage of identification with material life. It is through devotional service to God that I personally find peace.
Mantras are of all different varieties.
They are aimed at many levels of divine consciousness, and they are not all equal. In various parts of the Bhagavad Gita, Krishna tells Arjuna that less intelligent people worship demigods. He instead advocates that Arjuna enter into devotional service to Himself, Krishna, because it's a higher calling, not aimed at improving one's own life here. So I say to everyone, think about your motivations. You cannot protect your live's here.