There's a brief line in Genesis that says volumes. In 18:12, "Sarah laughed to herself," after hearing that she was supposed to have a son in the coming year. So often Sarah's laughter, her disbelief, her lack of faith resonate when the impossible calls out. When logic decries the direction of my heart, I think of Sarah and her laughter. (Even if my own laughter is more of a hysterical giggle.) Sarah laughed at the impossible.
She tried to apply logic to the issue at hand--- namely her own lack of issue. Her effort to figure out how to fulfill God's calling Abraham to fatherhood was, well... disastrous and with consequences reaching far into a future lacking in peace amongst the descendants of Abraham borne to him by Hagar and Sarah. Those consequences (an epic fail) help to stay my mind when I begin to try to think through the How of whatever God has called me to on any given day.
Rather than laughing at the impossibility of a given situation, perhaps one day I will be more like that Proverbs 31 woman in verse 25 as, "...she smiles at the future." The verse implies a sense of peace rather than the disbelief of incredulous Sarah and I.