One can no more keep the mind from returning to an idea than the sea from returning to a shore. For a sailor, this is called the tide; in the case of the guilty it is called remorse. God stirs up the soul as well as the ocean.
Anyone who refuses to marry is shrinking his farmwork, wasting the seed, and leaving idle the appropiate tools created by God; he sins against the purpose of creation and wisdom visible in the evidence of natural structure. The man who refuses to marry has severed a chain of being, a previously unbroken chain linking his own existence to that of Adam.