A common but short sighted interpretation of karma (also common psychology btw) is as follows:
They’re hurting because it’s their karma (aka their fault). I’m hurting because it’s their fault. I’m happy because of my good karma (aka I did well). They’re happy because things went well for them.
This is easy because it only makes the good things that happen to us OUR business, while it makes the bad things that happen to us the result of circumstance. This would be fine if we thought the same for other people, but generally we don’t. Generally we blame others more easily than ourselves, both for the bad that happens to them and the bad that happens to us.
An expanded version of this post appears in my book Essays on Karma.