Why high expectations may lead to lower achievement

I’ve always believed in setting high expectations.

Because why not?

Here’s how I saw it:

If you set and reach high expectations, that’s awesome obviously. And true, you might risk disappointment if you fall short, but you also probably achieve something greater than if you set (and met) low expectations.

This is in favor of being small fish in a big pond, rather than the big fish in a small pond.

Whereas the only reason to set low expectations seems to be this: To make sure you meet them and so lower the risk of bruising your ego. Sounds egotistical to me.

Or so I thought.

Currently reading Your Brain at Work. And here’s what it says about expectations:

• Met expectations generate a slight increase in dopamine, and a slight reward response.
• Exceeded expectations generate a strong increase in dopamine, and a strong reward response.
• Unmet expectations generate a large drop in dopamine level, and a strong threat response.

I thought it was just ego. But what actually happens is this:

High expectations, which high achievers are prone to set, tend to become unmet expectations. And unmet expectations drop dopamine a whole lot. The drop makes your brain feel threatened, making you feel frustrated and likely to be a lot less effective.

High expectations -> disappointment -> Drop in dopamine -> Inability to think and work effectively

So I was wondering: Does inability to think and work effectively ultimately lead to lower achievement? Or screw that and Reach for the moon. Even if you miss you’ll land among the stars?