There is a power in positive thinking and even if you are a skeptic it is a bit like the the quote about life.
“Life is great when you consider the alternatives.”
While positive thinking isn’t sufficient by itself it is a good start and when done right it is a lot better than the alternatives.
Try the Positivity Challenge.
Positive thinking is an element of Stephen Covey’s first habit of self mastery, “Be Proactive”. A positive attitude allows you to be prepared in the gap between stimulus and response to make a choice that will have a greater probability of a positive outcome. A fundamental starting point is that decisions you make matter. This is not to say that you can control the world but that what you think and do does make a difference especially for you personally. This is not merely wishful thinking. To have a successful action plan it needs to start with thoughts of possible positive outcomes.
In the debate about fate vs. free will it seems to me to be a better bet to act as if free will exists. If everything is determined by fate you are no worse off if you act on a belief in free will. On the other hand if it really does matter that you exercise free will to influence outcomes even a little bit it could be disastrous to be unmotivated and leave it all to fate. Just because you are only one of many factors influencing future outcomes that is no reason to drift. Just try and with the feedback try again. We all can make a difference.