If you are focused, disciplined and ambitious, I'm talking to you. I'm no expert, but I'm going to give you some advice anyway.
Have more than one thing going at the same time. Continue on with your big project. By all means concentrate on that.
But splitting your focus can be useful. Here is what I mean.
You are a painter and are working on a large commission. Have something small and personal going at the same time. A tiny painting, or better yet, a sculpture comes to mind. Something people won't pay you to do. Work on that when you need a break. Do that instead of checking your Facebook feed. Do that instead of over-working your painting.
You're in training for a marathon. You are disciplined and have a regimen. Remind your sporty self that you are capable of more than one modality. Do something slow. Tai Chi or yoga. Better yet, go to a diner and linger over the book you don't have time for while you're running. Order a cheeseburger and fries. It won't kill you. And if you're worried that it will, you may want to re-think that marathon.
I'm not suggesting that you do this daily. Once in a while, shake it up. That's all I'm saying.
When I was a still life photographer, having a part time job on the weekends turned into more than the sum of its parts. The job had nothing to do with photography. That was the best part.
If you are a Stay-At-Home-Mom or Dad, you're really busy. I'm going to suggest something else anyway. Even though you're not getting enough sleep and haven't had a shower yet, squeeze in something else. Start small.
If you are already blogging about being a SAHD or SAHM, then you need an additional something else. At least one more something else. If you are crocheting darling baby booties and making a killing on ETSY, you too. One more something else.
It should be selfish, smart and not family friendly. Volunteering at school doesn't count. Your kids are growing fast and someday they will be adults.
You're in business. You do business type stuff every day. Wheeling and dealing. Raking in the bucks. You're confident and hitting your stride.
Your something else should be something so new that you don't know what you're doing. It can be anything, as long as you start out crappy at it. Do it a little at a time and get a little better every time. Knock yourself down a few rungs. Start at the bottom. Let the other people doing it shine. You don't need every accolade.
I don't want to bash Gwyneth Paltrow. I wouldn't do that because I happen to like her. I like Goop. I'd really like bargain shopping to be her one more thing. That, and a sense of humor.
I suggest that she shop exclusively at the 99 cent store and then decorate some rooms. There are some real treasures there if she would just look for them.
If you've been laid off and are looking for a job, have more than one goal for your period of unemployment. That piece of advice was in the 1994 edition of What Color Is Your Parachute and it stuck with me.
One cautionary tale: don't let the other thing that you cultivate get in the way of your big goal and become your license to procrastinate. The main thing is to keep the main thing the main thing. Stephen Covey said that in The Seven Habits of Highly Effective People. That stuck with me too.