"My soul is silent before God" (62:1).
"My soul, be silent before God" (62:5).
The verses are similar, but different. In the first verse David says something about his soul; in the second he says something to his soul. The phrase, "is silent" addresses a decision, a settled state of mind. "Be silent" is self-talk, David stirring his soul to remember that decision.
David speaks first of his determination to live in “silence,”—quiet submission to God's will. This is our calling as well, the thing for which we were created. You and I will never be at peace until we've settled this issue: "Not my will but yours be done." This is our first and highest calling as God's children and the source of our deepest pleasure. “I delight to do your will,” the psalmist said (Psalm 40:8). "It's chocolate," the fair Caroline says.
But "the air gets thick in Narnia," so we must "re-up" all through the day, "Hey soul!" We must say again and again, "Be silent (submissive) before the Lord."
That's because God's will is sometimes hard. He asks us to do difficult and dangerous things because they're the right things to do. He calls us to endure hardship without complaining, to love awkward people, to heed the voice inside us that says, "You mustn't," to take steps we'd rather not take. So we must preach to our souls all day long: "Hey soul, listen up. Be silent: Do what Jesus is asking you to do."
We must always ask for God's help, of course, for "our hope is in Him alone" (63:5). When we ask for His help He delivers it, for God never asks us to do anything that He will not or cannot do.