I love this Steve Jobs quote as well as some of the others.
"People think focus means saying yes to the thing you’ve got to focus on. But that’s not what it means at all. It means saying no to the hundred other good ideas that there are. You have to pick carefully."
"It's simply a matter of doing what you do best and not worrying about what the other fellow is going to do."
Sir Winston Churchill
"It is a mistake to try to look too far ahead. The chain of destiny can only be grasped one link at a time."
Thomas Jefferson: Inspirational Quotes: Focus Quotes
"I'm a great believer in luck, and I find that the harder I work, the more I have of it."