Leaning On the Wrong Supports

Isaiah is prophesying against the Israelites who, when threatened by the Babylonians, went off and tried to set up a military alliance with Egypt instead of relying on God. (He later described the Egyptians as a splintering reed—a walking stick that would collapse when they leaned on it.)  

The still small voice of the Holy Spirit speaking to the people called them to repentance but they wouldn't listen. Later, in the same chapter Isaiah admonishes them with the following words:

"In repentance and rest is your salvation,
in quietness and trust is your strength,
but you would have none of it.
You said, 'No, we will flee on horses.'
Therefore you will flee!
You said, 'We will ride off on swift horses.'
Therefore your pursuers will be swift!

We cannot ask for God's power until we stop relying on other sources of strength. We cannot ask for guidance if we plan to go our own way. We cannot expect that the Holy Spirit will always lead us along paths that seem obvious to us. 

In Ch. 55 Isaiah says this:

 8 "For my thoughts are not your thoughts,
neither are your ways my ways,"
declares the LORD.
9 "As the heavens are higher than the earth,
so are my ways higher than your ways
and my thoughts than your thoughts."

God has an awesome plan for our lives. The Holy Spirit will guide us in the fulfilment of that plan. If we ignore His promptings, we will not only miss out on God's plan, we will sin and walk in the darkness.