I never said negative thinking is overwhelming. I think it's exactly the opposite. Once you can come to terms with your worst-case scenario (ie. quitting and getting a job again when it fails), it frees a lot of burden and helps you work harder.

There is no issue here, merely semantic confusion: we're using the phrase "negative thinking" to mean different things.

Think of it this way: planning for negative scenarios is generally implies that you're willing to deal with them. To be willing to deal with them, you probably think that you're capable of dealing with them.

Even though dealing with negative situations isn't kittens-and-puppies happy, it is solidly optimistic. That's the kind of positive thinking that helps you.

Good summary.