자신있다(ja-sin-iss-da, jasinissda)
Used when feeling confident and capable about something
When to use
Job interview prep, Presentation confidence, Sports game confidence, Expecting exam success
The nuance
자신있다 indicates a positive mental state, used when you believe you can do something well.
자신없다(ja-sin-eop-da, jasineopda)
Used when feeling uncertain or lacking ability about something
When to use
Job interview anxiety, Presentation worry, Sports game fear, Exam failure worry
The nuance
자신없다 indicates a negative mental state, used when you feel you might not do well at something.