Positive thinking can set you up to fail if it creates complacency and inaction.
There is a difference between positive thinking and optimistic thinking. Bottom line is that action is required to do something about your ideas and whatever energizes you to take action is what will help you achieve results. Personally I prefer energizing action through an inspirational vision of the possible future rather than a fear of a potentially disastrous future. Advance towards the light instead of fleeing from the darkness.