The Buddha cannot take away our negative karma; it is up to us to do the practice. An analogy illuminates this situation. Imagine a person standing in a large open field with a tent in the middle. Suddenly a huge hail storm pours down and they have the choice of running around the field and suffering or entering the tent for protection. The field represents samsara and the tent, the practice of Dharma and the Three Jewels. If the person does not enter the tent of practice, the Buddha cannot protect them from samsara.
So it is in our hands to take up the practices that lead to full awakening. And the first stage is going for refuge with our whole being to what is the most precious, the Three Jewels of the Buddha, Dharma, and Sangha.
~Karmapa: The Torch of Certainty, Session 1