Proverbs 28:26 Whoever trusts in his own mind is a fool,
but he who walks in wisdom will be delivered.
Trusting in your own mind, in your own heart, is the opposite of trusting in the Lord. Look at the contrast: be a fool or be delivered. Remember the words of Proverbs 3:5 and 6?
Trust in the Lord with all your heart, and do not lean on your own understanding. In all your ways acknowledge him, and he will make straight your paths.
So why are we all so prone to keep on trusting in ourselves? Jeremiah 17:9 lends some insight-
The heart is deceitful above all things,
and desperately sick;
who can understand it?