You could say that you enjoy challenges and love the feeling of satisfaction you get from producing great work even though it may have been difficult and there may have been intense pressure. It would also be good to mention that you enjoy working as part of a productive team and contributing to successful projects. You could also relate what motivates you to the specific requirements and duties of the job you are applying for. Think about what key skills are required by the job you are applying for and try to demonstrate that your motivations are the same. If you can, try to show that you are self-motivating. Give examples of times when you have motivated yourself to achieve success, for example: completing university coursework, setting up your own business, or organising a sports team. You do not want to appear as someone who always needs someone else to tell you what to do to get you motivated. Show that you are prepared to push yourself for success.