Psalms today points out that there is only one God who reigns supreme:  

Psa 18:31  For who is God, but the LORD? And who is a rock, except our God?—

The metaphor being used there is a rock, or something solid and unshakeable and that is how David describes God, as constant or unchanging.  

We are always wishy washy in our ways forever changing our minds to best suit our own purposes, but God is now what He is always was and always will be.  

We humans will come and go, but God is forever!