As you sow, so shall you reap.

I'm inclined to say this means that our our actions today will determine most of our experiences tomorrow. We cannot say that everything comes by chance because we are in some measure of control to what we are going to go through. Some things are beyond our control, but most things happen depending on our action. In other words, nothing happens for no reason - it's usually because of something we did or something we let others do to ourselves.