We all begin from where we are. When we believe in God, we believe as we have come to understand both what it means to believe and as we have come to understand what God is. But what it means to believe and who God is that we might believe in Him are really only extensions of our own human experience. This is especially true of religion revealed in writing, in words. Words must be learned through human experience, and so reading even revealed words, we can only understand them in terms of our human conceptualization of those words. That is, we take our experience and amplify it: God is man in capital letters (God = MAN).
God accepts this. God accepts everything we offer him, no matter how misguided or misconceived or limited it is--God loves us that much. But because God loves us that much, He does not let us stay in our misconceptions. God breaks out of every conceptual box. And it is perhaps this continual experience of God not remaining quietly in the box we have prepared for Him that leads us to the knowledge of God beyond knowledge: a rather intuitive knowledge that makes use of conceptualizations only metaphorically.
A big part of our experience of God's breaking out is experienced as painful suffering. God doesn't do what we expect Him to do. God doesn't answer our prayers as we expect Him to answer. God allows the ungodly to triumph. God takes away from us all that we had been depending on, the certain pillars of our life, of our faith, of our reality. Everything is shaken so that only that which cannot be shaken remains, as it says in Hebrews.
And what remains is a deeper knowledge of God, a knowledge transcending knowledge. God is nothing like man; rather, the likeness is not because God is the ultimate human conception, but because man is a divine conception: man is God in minuscule: (man = god).
A lot of this shaking results in seeing ourselves more clearly, seeing the foolishness, vanity and fantasy that we have clung to as reality, that we have believed and fought for, and through which we have wounded ourselves and those whom we love. This is the real pain of suffering, but it is a suffering that does not lead to despair, for in admitting what has been false, we come to see and then cling to what is true, to He who is true.
I think this is the wisdom of the Church in teaching us to pray, "Lord have mercy!" We do not know what needs to be shaken in our life and in the lives of those we love. We do not know what it will take for us to see and cling to the real, for those we love to see and cling to the real. But before we can pray "Lord have mercy" with an open heart, we have to let go of our fear of pain--which is really only the fear of death: pain being death on the installment plan, as someone once remarked. But not to fear death we must really believe in resurrection. We must really believe that pain is a door through which we enter life, or through which we may enter life, for not everyone who suffers finds life, which I think is a kind of hell: suffering with no meaning, no telos, no end.
But if we believe in the resurrection, then we have hope. We have hope not only in our own suffering, but in our shared suffering, in our suffering with the suffering of those we love. We can say "Lord have mercy" as a prayer full of hope, full of faith in the God of resurrection, the merciful God who loves us much, much more than we can ever love, who loves beyond our conception of love. Then we can thank God for all things. Then we can rejoice in every no as a yes from God.