Life is absolutely more than positive thinking, it is living for the purpose. You can be very positive today and something bad happens to you tomorrow, like eccle 9:2 will say: "all things happen to all men alike" but the truth is the outcomes are not the same. What makes the difference is no just in your thinking (though plays a major role), it is in fulfilling the God given purpose. Everything happen to all men alike but the outcome is different for a man that builds his like on the Word of God just like the persons in Matt 7:24-27, both built, both had same challenge, but one was still standing because of what he built his life on-and that's on Christ.
Therefore I say, it is good to think positively, but better to have a purpose driven life( founded in Christ) which brings the most satisfaction and fulfillment .