The wayob is the animal spirit inside every character in Itza. As a character you are born with it, and you can learn to tap into the immense power it can grant you, but such power also poses great risk. Tapping too much or tapping recklessly can make your character succumb to the animal nature of the wayob.
Wayob powers are tempting as the game mechanics allow you to succeed while failing. This presents a great temptation as you can try to tap into powers way beyond your character's reach and preparation, and still succeed in triggering them. As a player I can deliberately try to tap into a power far too strong for my character's skill level, a power so strong I'll certainly fail in invoking. Yet it will succeed. How is this? Simply put, it's the animal within your character taking over and turning a success into a failure. My character isn't very skilled, but wants to grow bat wings and fly out. Such a task is beyond the character's current skill, I roll and get a terrible outcome and my character grows wings and flies out. What happens is that it's the bat within my character flying out and taking temporary control over my character.
This control can affect the character physically and mentally as well as affect fellow party members. There is nothing stopping the bat within turning against party members and draining a fellow player's character dry. Your character may also start to develop permanent physical changes such as fangs, leathery skin, strange eyes, etc., changes that may pose risks in towns and cities afraid of such creatures.
Overall, the final result is a grey zone of failure bordered on both sides by a zone of success when the character can control the wayob and a zone of success when the character can not control the wayob. Yielding control to the wayob can be tempting for a short term benefit with a superb and uncontrollable power.
How much are you willing to pay to gain such an advantage? As a player it may be seem ok to tap into such immense power once to save the character, but if you know there's this "safety net" wouldn't you be tempted to run greater risks in the adventure which may corner you to tap into uncontrollable wayob powers more and more often? Can you, as a player, roleplay the wayob against your own character's interest?