The other is that we realize that we cannot guarantee our security, and so we feel anxious. Pride is anxious about the future. I, even I, am He who comforts you. Sounds strange doesn't it. But that's how subtle pride is.
Pride is the root of our anxiety.
Casting your anxieties on God means trusting the promise that he cares for you and has the power and the wisdom to put that care to work in the most glorious way. That trust is the opposite of pride. It's the essence of humility. It's the confidence that the mighty hand of God is not over you to crush you but to care for you just like the promise says. Don't be proud, but cast your anxieties on him because he will care for you.