Over-confidence is premature death. One incurs danger by over-confidence, If one trusts another completely, he is said to live by the favour of the trusted person.
अकालमृत्युर्विश्वासो विश्वसन् हि विपद्यते। यस्मिन् करोति विश्वासमिच्छतस्तस्य जीवति॥