One goal at a time-- That's important. That is where most people unwittingly make their mistake. They don't concentrate on a single goal-- at a time-- long enough to reach it before they're off on another track, then another, with the result that they achieve nothing. ~Earl Nightingale
It is important to realize you will never reach success without creating goals. I am a big advocate of writing your goals on paper. When you have done that, it is also important that you concentrate on completing your goals one at a time.
There are countless studies that show multi-tasking is not an effective way to get things done. If you need multiple things done concurrently, delegate responsibility to those capable of doing the job. Yes, that takes manpower. In reality, I see flawed work every day in business because people are being pulled in too many different directions. Things are more likely to slip through the cracks. So many things are left incomplete or never even get off the ground because of this.
Earl Nightingale was a smart fellow. His advice is that we work on our goals one at a time in order to actually complete them. It takes determination, endurance, discipline, and patience.
In my business management experience I have seen more companies in recent years become inefficient as a result of increased multi-tasking. Cutting the workforce can be good, if you remove non-essential people. When you cut a workforce to save money and it hinders productivity, there is a problem.
For the freelancer, you must be able to keep your pipeline full of projects; however, there comes a time when you cannot take any more work unless the client is willing to wait in line. If you have reached that level of fame-- that is, people are willing to wait for you-- you won't lose anything by working on one project at a time through completion.
If you must do more, surround yourself with talented people with whom you can coordinate efforts and draw up a nice contract agreement to protect all parties involved, then go for it. If not, then you must learn to say "no" before you bite off more than you can chew.
One goal at a time is your ticket to success.