Let's take for example a gossip that has spread at work, do you always believe in these gossips or do you refrain for believing in them because you didn't actually saw them happening. In cases like these, you must ensure that you saw the action before you go spreading the gossip and making matters even worst. Gossips are tricky methods people use to get others and you into trouble.
Another classic example of when you apply what you believe vs. what you see is in religion. All religions are controversial in their own way because of what each group believe . Are you religious? If you are, do you believe in your religion's practices and beliefs based on what you see or what you believe? With religion and maintaining a high spirituality, you always guide yourself by what you believe and nothing is wrong with that. To believe in God you don't necessarily have to see him, all you do is believe in him.
All I am saying here is that you must know how and when to make decisions by what you see or what you believe, especially in your workplace. Follow the heart, it always helps.
What do you base your decisions on?