" It can be invigorating with good instruction, or terrifying if your gear"

is not set up properly. This is the only time you're completely dependent on the gear,

So you need to know all the different ways to safely set up a rappel or trust that your instructor knows how to. At crags or sport routes, most times there will be a top bolt you rap off of -- again, check the quality of any and all anchors before setting off.