"Decisions Determine Destiny" means that your decisions make an output, which is your destiny. So depending on every single decision, there is a different path to the future. Every single decision has it's own path and consequences.  Every decision, big or minor, still impacts you. Even a small decision, like deciding to buy a bag of chips to eat as a snack, or to decide weather to get married with that perfect person, you are creating different outcomes in your future. In the case of buying chips, you just spend money on something that would increase the chance of cancer. For the case of marring that perfect person, you may have done a bad or good decision( depending on how your marriage last or any other thing).  So imagine every decision you have ever made in the past. There was suppose to be millions of millions of outcomes for all of the decision possibilities in your life. So right now you are following only one path out of the other possibilities.