Individual differences in SLL(second language learning)

 In 'Understanding Second Language Acquisition' class, I learned about the differences between individuals in SLL. As a second language learner(english), this chapter was very interesting to me. In this chapter, it talks about  many aspects like intelligence, aptitude, and learning styles.
 At the end of the chapter, it says that their aren't absolute factors that can lead you to failure or success in learning English. It a little bit disappointing that the conclusion is so uncertain, but now I believe that what it means is that people can learn languages regardless of their conditions.