We must not rely on our understanding.

Those wised Christians who have wrote the God’s commands on the tablet of their hearts and keep them

Trust God with all their hearts (Prov. 3:5-6). 

Here the word ‘Trust God with all their hearts’ refers to the ‘exclusive trust.’

This kind of trust is ‘Childish confidence” (Park Yun-sun). 

Believe in God like a child with simplicity of trust in relying on Him completely

is trusting God with all our hearts (Park).

In order to trust God with childlike trust, we must not rely on our own understanding.

The more we rely on our own understanding, we cannot trust God with simple heart like the child.