It helps me to look at my goals in big chunks (this quarter, this month, this week) and then set appointments with myself to actually do the work to get those goals done. So in this way I become my own client. Then I can give realistic responses to other clients' requests for information and appointments.
There are times when I move the appointments with myself around or cancel them, because I don't want to get too rigid about this. But if I don't block out some time ahead of time to attend to the non-client request stuff, I never get to it at all!
Before starting this plan, I used to think I would get 435 things done "by Aug 1." When I actually pull out the calendar and start looking at the time slots I have open I realize that I'll be doing great to get 11 of those things knocked off...So I've become a good prioritizer and am working on "letting go" of those other 424 things.
I guess the mindset shift for me has been "My business is one of my clients, not just the people who hire me." So my business needs my time, and the way I make this happen is to block it out on the calendar (usually on Monday for that upcoming week.)
This isn't a perfect system, but it helps me feel a little more sense of control.