It´s difficult to learn if the challenges you meet are too big.
Challenges should of course suit your age and intelligence. We are born with different kinds of intelligence (‘multiple intelligences’) and there´s a great diversity in where each of us is smartest. Someone may be super math-smart, but find it hard to figure out how to relate to others (‘people smart’ – social intelligence). Another person might be smart at words and language, but is not very ‘body-smart’. Some are fortunate to be born with a very big ‘intelligence-pie’ (super-intelligent), while others have been less fortunate and struggle to do many things.
It´s fun to learn when you are challenged in a way that fits your intelligence. You experience becoming better and it gives courage and desire to learn more.
If challenges becomes too big, and you are perhaps scolded or bullied, you lose your good spirit. Then the brain’s alarm centre takes over and the thinking brain is turned down (see here) with the result that it becomes difficult even to use the intelligences you actually have and it becomes twice as hard to learn something new. It´s a vicious circle.
If you practice what you are already good at, it becomes easier to learn difficult things, because the thinking brain opens up for new learning when you are happy and feel that it pays to practice