My wife, an experienced nurse, recently switched jobs. The change had been a long time coming. Jana was excited to join up with two doctors whom she had worked alongside previously. She was back with "family"; she had come home.

Her first evening at the clinic a young mother came with her 18-month-old son. He needed his final shot for a routine immunization; his mother came for a physical. Both patients were new to the clinic.

Jana gave the boy his shot, and his mother took him back to the waiting room, where his sister and grandmother sat. The mother then went back to the room for her physical. When Jana went to record the vaccination on the boy's chart, she noticed that the seal on the vial inside her lab coat was unbroken. Quickly Jana realized that she had given the boy the wrong vaccine.

She had given him a shot from a different vial—a routine vaccination for children, but the boy had already completed that series of shots months earlier.

Jana told me she gasped when she realized her mistake and then went into shock, physically numbed by the fierceness of what raged within. Here is the sequence of her thoughts, according to what she told me later:

"No one will ever know. No harm done."

"I can't tell the doctor."

"This is my first day on the job."

"The doctor will think I'm incompetent."

"It can't hurt him, can it?"

"It doesn't hurt to be immunized twice for the same thing."

"But he needs the right vaccine."

"What will the mother say?"

"But I will always know, and so will God."

Meanwhile, the doctor was examining the boy's mother. Jana weakly paced outside the room.

Much of Christian character is formed in these ordinary but weighty, internally unbearable moments. Following Jesus, though, is often cast as a series of big things: the big decision to be more committed, the big decision to forsake all and become a missionary, the big decision to become a pastor, the big decision to do big things for God.

At stake, perhaps, are future big decisions. Yet the real battles are often fought internally, in quickly passing moments.

When the doctor walked out of the room, Jana told him her mistake, almost vomiting her confession. "Whoa. Let me think about this for a moment," he said. After a few moments, he walked back in the room, told the mother what happened, and asked her to schedule another time for her child's immunization. Jana's anxiety released, she was now free.