why some individuals are more successful in learning a second language than other individuals?,,, help me.

1) internal factors
Some individuals have the tendency of faster language learning because of their own intelligence or brain capacity. People that are smarter or have a healthier brain tend to learn things faster. These are also shown in their learning habits and their commitment.

2) external factors
Some individuals who attend courses or schools learn languages faster than those who study on their own. People around them, or their social motivation may boost their commitment in language learning.
The person's origin could also affect them. For example, someone living in China won't really have a hard time learning Japanese as Chinese and Japanese language used to have the same words and roots.