Many politicians that reach high levels have something inside them that convinces them they're fighting for a higher cause and that their enemies are on the side of evil.
Franklin Pierce was no exception.
An obscure politician from New Hampshire that had the right combination of being able to bring home Northern votes as well as a suitable party loyalty to the Democrats and their Southern power base. Beyond being in the right place at the right time, I wouldn't call Pierce a masterful politician, but he sure thought he was imbued with a God given sense of purpose that propelled him to the highest office.
Tragedy struck his family when his son died in a railway accident a few months before his inauguration. Looking at the glass as being half full though, his wife convinced him that God took his son away from him so he wouldn't be distracted from his quest to rescue America from the evil doers. When his wife suffered from 'melancholia' (depression) and became a recluse, I suppose he saw that as a way to let him focus on his work as well.
Like the football player who thanks God for helping them make a touchdown, Pierce seemed to think that God took a personal interest in his political well being.