There are three things people strive to do what they do for:
Identity
Security
Stimulation
If you are going to sell something, be it an actual product or an idea, you must know what your product is! The product is what you present and give someone, not you or your ego, even if your product is intimately tied up with your product/pitch.
People will do much for you, and be very forgiving, if they like you. The most important reason people like others is because they think the person they like cares for/about them.
Figure out what you are good at. Follow that, work on that, capitalize on it. The things you are not good at, don’t do and don’t worry about it. Figure out how to get others to handle that part for you or, just don’t do that. Good managers are folks that can see what people working for them are good at and facilitates their focusing on those tasks.