Karma is an interesting topic.
Personally, I dont often think in terms of 'karma' but instead I think in terms of our own lifes paths, everything happening exatly as it is meant to.
The universe doesnt give us any more then we can handle and it is up to us to find the strength to live the tests or to give up. Sometimes, we dont finish the test and knowingly say no to completing it. We can do that, but it means that the test will come again and often it is harder.
As an example I had a friend that was very giving in fact, I would say she gave too much of herself to others. Then she fell in love and he hurt her very deeply, but she didnt stop pursueing him. Months past and it happened again, but on a much grander scale. She learnt then to hold back a little, and shield herself because not everyone has good intentions. I think though it was a harsh lesson to learn, it was needed and she made need this lesson in the future..
Bad things happen in your life and good things if we are lucky (but to be honest? I think it isnt bad or good. it just is..). It is how you deal with it that counts..