One of the thing i keep running in to is that when you say to quickly yes, things don't get exacly to where they need to go. But saying yes can give a lot of new opportuninties, but it's get down to know when to say yes and now. A video below of Steve Jobs about focus can help you a get started.
A more compleet version can be found on a article at TechCrunch.
Another great video is the following one.
Apps and Addons for webdesigners, webdevelopers and business owners