What might motivate a character to do something so deceitful

There are many reasons why a character might decide to do something deceitful. For example, the character might feel that doing the honest thing will bring him problems. Therefore, being deceitful might feel like a better option for him. Another reason could be that the character is being deceitful in order to protect someone he cares about. Finally, a character could be deceitful because he wants to harm another one, or because he wants to obtain something he cares about, regardless of the damage he might cause.