Wicked Wednesday - tips for multi-tasking manuscripts

That's how I look when I try to do more than one thing at a time. I'm one of those writers who focus on one project and finish it before diving into a new one. Most of the time, I'm highly efficient. So does that make me crazy to want to attempt to work on two projects at once?
I see other writers who are brilliant at multi-tasking projects. I am in awe. But I know all of us are different. What works for one person might not for another. We don't know until we try, though.
Two projects. Yikes. I'm taking a deep breath here. I'm collecting advice from other authors who are successful multi-taskers.
- Create a schedule and stick with it. Sounds easy, but what if you're on a roll? Too bad. Stop and continue again tomorrow. Be firm with yourself.
- It helps if your projects are vastly different from one another. That way, you won't get tired of too much of the same thing.
- Keep writing. Don't edit as you go. Leave that for the revision stage.
- Don't neglect other aspects of your life. Make sure you have time to spend with family and friends, exercise, and sleep. You will be a happier writer for it.
- Finally, finish what you start. If you find your focus is off because you have too much on your plate, drop one project. 
Do you have any tips to share about multi-tasking projects?