Self-doubt (noun)

Uncertainty or lack of confidence in one's own abilities, qualities, or judgment.

Origin:

Self-doubt is derived from two words: 'self', meaning 'the individual person as the object of his or her own reflective consciousness', and 'doubt', meaning 'a feeling of uncertainty or lack of conviction regarding one's beliefs, opinions, or abilities.'.

Examples:

1. John struggled with self-doubt after he failed his exams.
2. The writer had moments of self-doubt, wondering if her work was good enough.
3. The actor's success was not enough to dispel his self-doubt.
4. She struggled with self-doubt in her abilities as a leader.
5. He had a constant feeling of self-doubt about his career choices.