One of the most successful people that I know currently has a Warren Buffet quote as his Whats App header. Warren said that, " The difference between successful people and really successful people is that really successful people say no to almost everything."
Given that Buffet is objectively the most successful investor ever and my acquaintance owns over 40 companies internationally and so is hot on Warrens heels I figure that this is probably good advice.
I think however it could be qualified as the relationship between opportunities recognized and opportunities acted upon.
Given that the world is full of opportunity and highly successful people both get to see more and are better at recognizing it, they have to be economic in what they act on or they would be overwhelmed and their results diluted.
Unsuccessful people probably don't see much opportunity and wouldn't act on it anyway.
With increasing success comes increasing opportunity and the key I think is to keep your powder dry until you see the best ones and only act on them.
So, to increase your success start to generate more opportunity and become much more picky about where you place your resources.