According to Buddhism, the cycles of cause and effect of our negative deeds (karma) yield only pain. When we die and our mind escapes from the web of our material body, we begin our journey through the transitional state (bardo) to our next rebirth. Whether our subsequent rebirths are pleasant or not depends on the habits that we have generated in our mind. Whatever negative experience we have today is the product of some unwholesome mental and emotional tendency, or karma, from our past.
Karma can also work in our favor, however. Thanks to karma, if we could sow a seed of positive perceptions and feelings, we could turn our mental and emotional tendencies to positive ones and start to enjoy a peaceful and joyful life.
Source: The Heart of Unconditional Love