An internal conflict is a problem faced by a character inside his or her own mind. Some examples of internal conflicts are competing desires or priorities, tough decisions, and overcoming fear, addiction or bad habits.
An internal conflict is the opposite of an external conflict. External conflicts are problems faced by the character in the real world, such as a struggle against nature, society or another character. Stories often contain both internal and external conflicts. For example, in "The Great Gatsby," Gatsby faces an external conflict when Tom, the husband of the woman he loves, blames him for the death of a woman and her grieving husband kills him. However, Gatsby's main conflict is internal: his desire to return to a past time when he and Daisy might have had a future together.
Similarly, in Shakespeare's "Hamlet," Hamlet faces an internal conflict of whether or not to avenge his father's killer, but he also has an external conflict with the murderer himself, who has married Hamlet's mother.