I feel that the preponderance of so called positive thinking is to offset the power of negative thinking. The average person is overbalanced in negative thinking and need the positive to offset or try to correct the balance. This can lead to problems.
Positive thinking is not an end all. One may get just as overbalanced to the opposite spectrum and be naieve as you suggest. This is what happens when you work with the laws of duality though
An end all I believe entails going to the original plan of no judgment of bad, but also no judgment of good. Seems paradoxical but extremes of either nature throw balance off, the new covenant might entail well, no-Thing really just the knowing that by grace all is as it is and by knowing that simple thing that I do not need to judge, that all is already worked out. (and it is always for the good) for we may see that good and evil are abolished when we leave the old system of judgement law.