"... the fearful, the unbelieving, and the depressed ..." (Emmet Fox)
When I'm one, I'm all three.
Fear is depressing, and both come from a failure to believe in God's providence.
Solving the problem of unbelief is hard, until one realises what's in the way is belief, in oneself.
Eliminate the belief in oneself, and the space is created to believe in God.
I've never been (or met) anyone fearful or depressed who wasn't 'right' in my (their) perceptions.
As soon as I'm wrong, I'm free.