Fear & self-reliance

I can rely on God or self (ego). What for? Identity, purpose, and strength.

The Big Book says that self-reliance fails. Why? The ego's notions of my identity and purpose are rooted in the material world, are therefore susceptible to change, are therefore vulnerable, and are therefore sources of fear. Also, the ego provides only limited strength.

God-reliance works. Why? My identity is in God, and that cannot be changed or harmed. My purpose is to make a good effort today to do God's will. Nothing outside of me can affect my effort (though it may affect the result). God's strength is unlimited. My reliance is therefore on a strength that is unlimited, a purpose that cannot fail, and an identity that cannot be shaken.