Your brain is a powerful instrument. Ask it for reasons why you should hire someone and it will respond with answers like:
He made a great impression.
He seems to really want the job.
She’s got all the right experience.
Ask your brain why you shouldn’t hire the person and, again, it will give what you asked for:
He’s been out of a job for five months.
She didn’t interview well.
He doesn’t seem like a team player.
Knowing your brain can justify almost any action you consider, you must ask it instead, “What is the right thing to do?” And, after that, it is often still worthwhile to ask a co-worker (who doesn’t have the same vested interests as you) for his or her opinion. It helps keep you objective.