Affective factors definitely play a role in second language acquisition, research has confirmed that a variety of affective variables relate to success in second language acquisition.
This is Sparta
The Critical Period Hypothesis is the subject of a long-standing debate in linguistics and language acquisition over the extent to which the ability to acquire language is biologically linked to age
An interlanguage is the term for a dynamic linguistic system that has been developed by a learner of a second language (or L2) who has not become fully proficient
This video explains what Universal Grammar is in Simple Terms