Your evidence and conclusion would appear to be solid, but they aren't
entirely relevant to the point.
Although a 'positive mindset' doesn't increase your chance of success with
actually succeeding in a work project (like designing and manufacturing the
card), it makes a huge difference in marketing. In order to get somebody else
excited about a project, thus convincing them to invest, you have to believe
yourself it will work out. Otherwise, your words sound artificial and empty.
Hope that helps :).
