Two of these belong together, one does not. If you guessed sincerity and passion, you are correct. Any job worth doing, is worth doing well (cliché alert). When presenting or in conversation, you must believe in your product or service. If you don't, you didn't do your homework to develop a good product or service. When you are excited, people around you are excited.
It is too easy to cross over the line from passion to emotional involvement.
This can blind you to getting feedback on what you are doing. And cause you to drive over the side of the cliff. Marketing is full duplex and never let emotion cloud you abilitiy to listen to what others are saying.