"Prepare for the worst and hope for the best" is good advice, but there is a difference between hoping and expecting. If we expect unreasonable or unlikely results, we are inviting disappointment, depression and other negative thoughts, leading to unhappiness.
Thomas Jefferson said we had a right to pursue happiness, so it's okay to chase rainbows, so long as we don't expect to catch one. Sort of like a dog chasing semi trucks. He doesn't really expect to catch one, and we hope he never does (if we like him).
Sometimes we are led down the garden path by misleading advertising. A pill that will melt fat away, a food you can stuff yourself with and still lose weight. Exercises that are easy to do. (Hey, IT'S EXERCISE.) We all like things to come easily. No muss, no fuss, just problem free progress. Good luck with that.
On the planet that I live on, it often happens differently. For instance, we want our car repair diagnostics to be quick, accurate and simple. We are told that there are machines that we can hook up to a car, and it will tell us what's wrong and how much it will cost to fix it. That is complete crapola. Well, almost complete. There are machines that will give a well-trained observer insight as to the nature of the problem, but it still takes a diagnostician to interpret the data. An x-ray machine does not prescribe medication. It's a tool used by a diagnostician who can prescribe a treatment. A fingerprint does not incarcerate a felon. It is a clue used by a detective to investigate and solve a crime. Tools and clues are what mechanics use to solve the mystery of what is wrong with your car. The more complex cars require more complex tools, and more analysis of clues. Older people like to say, "My mechanic used to just listen to my '57 Chevy as I drove in and know what was wrong." I can do that. Just bring me a '57 Chevy, and I'll show you. But you're bringing in a 2007 minivan with an engine control module that is in charge of everything about the engine, and a body control module that controls everything from your windshield wipers to your headlights and air conditioning, with automatic sliding doors and a computer for the antilock brakes. That is a lot of things to listen to. It isn't as quick and simple as it was for a '57 Chevy, but the problems can be diagnosed by properly trained people, using expensive diagnostic equipment, if we show a little patience. Remember, the faster you make someone work, the more likely they will make a mistake. Expecting a snap diagnosis to be accurate would be your mistake.
Then there's the expectation of a "deal," usually defined as a discount. Let's start with a senior's discount. This rationale would indicate that an over age 65 party to a negotiation deserves a financial advantage over a party who is under age 65. Since I'm over 65, that means everyone should pay me more. They aren't lining up for that, for some strange reason. Actually I think the people most in need of a discount are the young couples trying to raise a family these days. They've got it really tough. In our business we do offer free labor to active duty members of the armed forces. They deserve much more than they're getting from our government, and they hardly ever play golf.
Finally there is the expectation that nothing on the car will fail in the future. When pigs fly. Businesses with fleets of vehicles establish maintenance funds, so that money will be available for the repairs when they happen, thereby avoiding the unhappiness of being unprepared. It would behoove prudent private citizens to do the same. Don't disappoint Thomas Jefferson, pursue the heck out of happiness.