When people suggest that everything happening in our lives is part of God's plan for us, it is just not accurate. In the grand scheme of things, we are to learn from our experience on earth, which experience is gained via our exercise of agency. We learn that good choices bring about good results and bad choices do otherwise. It is not as though Cain was supposed to kill Abel, that it was all part of his life plan. He was presented with circumstances where he had to make a choice. He ended up listening to Lucifer and following him. Cain was therefore convinced that his life would be better if Abel were dead. So, he made a choice to kill his brother. How did that work out for Cain? He learned by sad experience, not so good. He paid a hefty price not only for himself, but for his posterity. Cain could have avoided all that pain by keeping the commandments.

I agree that we are blessed when we keep the commandments, and that we are not so blessed when we do otherwise. The blessings and ill effects are not always immediate, but they do come. The plan is for us to learn the wise exercise of agency designed to lead us back to Heavenly Father. The consequences related to our choices are part of the plan designed to teach us in our journey; however, not everything that happens to us is some kind of predestined plan. If that were the case, then we would have no agency, but would be mere puppets moved about by the master puppeteer, and that's not how things work.