You have to be understanding of people's different mental abilities.
Stan is a teacher and has a poorly-performing student, who has some mental issues and tries very hard, in one of his classes.
Stan wants the student to improve.
Stan talks with the student and makes arrangements for the student to get tutoring.
Stan has a talk with the student and tells him to shape up and try harder.
The student slowly improves his grades over time.
The student gets exasperated and cries out of frustration, as he's already trying very hard.