At times though we can become obsessed with our karma wondering what previous action led to any number of things we're currently obsessed about: A disease we might be living with, a state of poverty or a perceived lack of talents. Believe me I've spent way too many nights wondering what I did "wrong" in a past life to develop a severe psychiatric condition but that's just not a good use of my time.
The problem is that karma is such an all-encompassing, timeless, constant process that it's nearly impossible to isolate what previous action led to a present condition that causes us particular suffering. There is karma at work that happened thousands of years ago. Plus, not everything is caused by karma. We know that the human form is the most suitable form to understand the Dharma in but it's not without its downsides. Some things, like sickness are just apart of the human condition regardless of who we were or are now as Buddha found out early: We get sick, we age and then die. So, it quickly becomes pointless to try and figure out what came from where. It will merely cause additional stress and suffering, which will do nothing to improve our current condition that we were suffering from originally before we started a forensic investigation into our past karma.
Physical disease is particularly hard to pin down because we are all destined for disease from our first breath as an infant. The minute we take our first breath, the countdown to death begins. That might be shockingly morbid to some of you but if you contemplate upon it you might find it frees you up to enjoy the present moment rather than obsessing about death and disease. We always seem to ask "why" when we have a major disease but not when we just have a simple sickness like a cold or the flu. Why, not? Because we simply understand that the human condition is frail and sickness is inevitable.
Yet somehow when we get a severe disease we think the severity means it must be punishment for something we did. The question becomes, "What did I do to deserve this?" The ego-mind wants some serious infraction to cling to because that would make sense to its limited and deluded nature but the real answer to that question of, "What did I do to deserve this?" is simply that you were born a human. That's it. I know, it's not a particularly exciting answer but that's the point. The ego-mind is looking for some exciting, unique reason for it. So, that even though the body is sick, at least it will get to feel important because some guru said the sickness was from some mysterious past life. It's silly isn't it when you think of it that way? It's not that we are trying to sound important--we just want to know why we're sick so we can feel better but the ego is so subtle that it can control us like a puppet and we're often none the wiser. That's why paying attention to our thoughts through meditation is so important. So that we can practice on being aware of our ego more and more.
This is important to remember when it comes to one's health because it can be easy to feel discouraged if we assume a disease we live with now is because of some terrible action we committed in the past. The point of Buddhism is not to figure out what we did wrong in the past but to stay centered in the present moment, so that we add as little additional burden to our karmic backpack as possible. Why worry if something in your past caused you to get sick? That won't help heal your disease but it will cause stress, which makes any illness worse. This reminds me of a famous lesson from Buddha, which goes something like this: A man gets struck with a poisoned arrow and the doctor wants to get it out as soon as possible and reverse the spread of the poison. Instead, the man shot by the arrow says first he wants to know who shot it, what kind of arrow is it? How was it made? Where did the wood for the arrow come from? Where did the poison come from, and what kind is it? But by the time the man finds this out he'll be dead.
Worrying about the past won't change anything--what's done is done. If you feel you did something less than helpful in a past life (or just yesterday) then don't worry about it; just live now the best way you can. Because you can't heal your physical self now without letting go of having to know all those "poisoned arrow" questions. Buddhism is about the present because it is the only time we have. We can waste our entire lives living in the past and I know some old people who have been lost to the ravages of that kind of worry. They are empty shells of people who are so balled up with stress and regret that they hardly know what is going on presently. They spent so much time lost in their past memories that even they have almost become a memory. Live in the now, not the past because we aren't guaranteed a tomorrow.