Concerns About Calvinism, and More Questions & Comments

Every Friday, we read your comments and answer your questions, always looking to the Word of God as our source of truth.  Although God's Word contains all the truth we will ever need to know, does that mean we have to fully  understand everything therein to believe it?  We subscribe to the doctrine of a triune God though we may not fully understand it; and we believe Jesus Christ is God in the flesh although we struggle to understand the incarnation.  So why do we feel we have to understand where God's sovereignty and man's responsibility intersect before we can accept God's great gift of forgiveness and justification through the cross?