I understand that whatever a person faces is related to some past life karma. But when the person is good in the current life, why should he or she face all those old painful karmas?
Just understand, you cooked food in the morning. By afternoon, you had forgotten that you cooked the food and found the food very spicy. Then you can't say, "Oh, I put spice in the morning, why is it spicy now?"
You ask this question only when you are in trouble. If you have invested your money and now it is giving you lot of benefit, you don’t ask, "Why is this happening. Why am I getting my money now?" You invested and the interest is coming now.
You sowed a mango seed and today it is giving you so many mangoes. You planted a coconut tree and it is giving you one coconut everyday now. You don’t ask why is it giving coconuts now? You planted some vegetables, and you will enjoy them when they grow. That time, why don’t you ask, "Why is God not in the present moment, and why is he giving me the beans I sowed three months back?"
Come on, wake up. Children are not born in one day. It takes nine months for a child to be formed. So time is part of this Universal phenomena. In fact, phenomenon cannot happen outside the dimension of time and space, and any phenomenon is karma.