nervous
worried about something /ˈnɜː.vəs/
confused
unable to understand /kənˈfjuːzd/
surprised
not expecting something /səˈpraɪzd/
lonely
feeling alone and sad /ˈləʊn.li/
Examples
"She feels nervous before exams."
"I am confused by this question."
"I was surprised to see her."
"He feels lonely sometimes."