God is the one we expect all good from and take refuge in during our needs. Whatever we cling to and rely on most is truly our god. Martin Luther wrote that our heart's deepest reliance defines what or who is god to us.
20. God is one from whom we expect all
good, and in whom we can take
refuge in all our needs….Whatever,
then, your heart clings to, and relies
upon, that is properly your God.
- Martin Luther, The Large Catechsim.