I don't quite agree for all circumstances. In general day to day behaviour, yes I would agree.
It is just that we have a limited amount of mental energy and have to choose where to dedicate it. That is the whole field of heuristics and biases. The thing I took away from Daniel Kahneman's "Thinking, fast and slow" is that while our brain is certainly capable of amazing rational thinking, most of the time we are not using that level, out of energy conservation.

There are mental shortcuts that are (or used to be at least) good enough to navigate day to day life with relatively successful outcome (like not dying).

In more abstract and complex fields these heuristics and biases are potentially not applicable anymore.

We like to think we are rational beings, while in fact most of the time we are demonstrably not making rational decisions.

Check out Dan Ariely:

BUT there are situations where hard things provoke curiosity and an irresistible challenge.
At heart we are problem solvers, where we enjoy the full unleashing of our rational mind with sometimes spectacular results. The trick is that you need to enter in a positive feedback loop that set this mental engagement in motion.

In fact, if it is too easy such activities are too boring, if they are too hard, we don't even try so it has to hit a sweet spot of difficulty, within grasp of our current competency but not quite.

Check out the Flow concept Mihaly Csikszentmihalyi :

Once you find such an activity, what takes over is intrinsic motivation:
A hugely important concept much more people should understand, Dan Pink has a masterful explanation about it: