"...it comes from saying no to 1,000 things to make sure we don’t get on the wrong track or try to do too much..." - Steve JobsThis quote is said so often that it starts to lose its meaning. So let me approach it from an angle that you may have never considered.
The greatest time management tool in the world is saying "no". We all want to do too much. We all want to say yes to our family, our friends, our boss or our customers. But every time we say "yes", we unintentionally say "no" to something else. And that something else is probably something that we already determined was important.
Figure out what's important. Schedule plenty of time - too much time - to get it done. After all, its important. And say no to anything that would take time from it.