All three types of karma (Sanchit, Prarabdha & Agami Karam) have a positive or negative effect on you depending upon the actions that created them. For example, if you have positive prarabdha karma you will have good things in life regardless of your present actions; you may do unwholesome actions and make others suffer, yet have a great life with all comforts of the world. But if you carry negative prarabdha karma to work out in this lifetime, then despite your good nature and all benevolent actions, you can have a life full of pain and miseries. Hence, there is perfect justice in ‘bad people’ having a good time and ‘good people’ having a bad time, each reaping the fruits of their respective good or bad prarabdha karma.
While you cannot avoid bad prarabdha karma meant for you to experience in this lifetime, the positive karma that you generate through your benevolent actions can act as a ‘shock absorber,’ thereby reducing its impact on you.