Life is complex with multiple goals.
Most humans handle simultenously, money, relationships, friends, physical state (food, sleep, exercise), and other goals.
Much of the problems of life management, are related to the overload of various goals.
Some would find it possible to be quite rational if they got only one goal in life. But there are many, and juggling all balls at once is much of the problem.
Science may contribute to this misunderstanding. By accident, actually.
Much of research is done by isolating a single problem and either finding extreme cases, or creating extreme situations experimentally.
Now as I explained, the inference from extreme case to the regular is not always reliable.
But in the general management of life it is much worse. If much of the problem is how to juggle all balls at once, how can we even start talking about isolated things?
We can learn about the mechanisms, we can learn tricks. But we much admit That much of the management problems is in the whole rather than the parts.