1. Karma isn't mandatory. There is this thing called free will. Free will complicates everything, but life would stagnate at all levels without it.
2. Karma works mainly at the soul level. The souls decide before each life what kinds of things they want to experience in that life, and that's the level where karma comes into play. It's rare to see karma working within one lifetime.
3. A lot of people try to think of karma as something that simplifies the way the world works. In truth, the world is complicated. Most people who believe in karma and deities and stuff do so to simplify things, which is incorrect. Life is just plain complicated.
4. Your soul is NOT your earthly consciousness. The earthly consciousness is a mask the soul wears in its game of mortal dress-up. The mask has its own consciousness and the soul merely watches what happens. It's always trying to talk to us and help us out, but most people don't listen. Or, at least, don't listen consistently. Again, free will kind of screws that up. The soul's goal is to get its mask to do whatever it is the soul wants it to do in a lifetime, without interfering with the mask's free will. Sounds pretty callous, and it bugs the shit out of me knowing this at times (I often angrily rail against my soul for various things) but the soul is such a fast-vibrating bit of energy that it can only experience the mortal realm vicariously through its masks. Through us.
EDIT: Adding this: It sounds kind of callous, this conception of the soul, but in truth the soul *does* care. It doesn't want us to suffer. That's why it tries to help. And it is ultimately a game, but a game with a purpose. The soul knows a lot, but there's a huge difference between knowledge and experience. The only way the soul has of getting experience is through us. So it's a learning process for all involved. And because the soul cares, I imagine it's pretty hard on them, watching us suffer and all they can do is talk to us, and we're quite free to not listen; to not listen so thoroughly that most of the time we can't even hear anymore, like tuning out noise as part of the background.
I imagine it does help somewhat that death, as we generally believe in it, doesn't actually exist. From our perspective it does, but ultimately it doesn't. Mostly because time, as we experience it, is an illusion. All moments are one moment. Sounds really simple on paper, but actually it's so complicated that I'm not sure any mortal could even understand it, let alone describe it.