An important skill to have when promoting your writing is dealing with rejections or bad news well. It's easy to become frustrated or even angry when you have a manuscript rejected, get some negative feedback about your work, or if you have a scheduled public speaking event or some bit of coverage in the media postponed or canceled. These things are simply going to happen--it's part of the business of writing. It's important to take them in stride and handle bad news professionally. You don't want to close any doors or burn bridges. When an opportunity falls through, be understanding and express an interest in pursuing it at a later date. Showing disappointment is okay, but keep it in check and put forth an optimistic face.
Remember: if writing is your career, then relationship building is an important part of that and having a good attitude in the face of set backs is essential. Always think long term.