This advice given to the former "yes-aholic", Shauna Niequist by her mentor, is one of the main premises of her book, Present over Perfect. After years of saying yes to too many things, she found herself unhappy, angry and tired. After much reflection she realized that she was trying to be all things to all people, saying yes out of the need to seek love and approval outside of herself. She wanted to be seen as competent and strong. However she realized that too many inauthentic "yeses" led her to a life that felt shallow. She now says that our best selves come from conserving and prioritizing our yeses, for the people closest to us.
"You can't say yes, without a no. If you're not careful with your yeses, you start to say no to some very important things (like self care, listening, connecting, etc.) without even realizing it."
Saying no is how we (especially the perfectionists among us) keep ourselves feeling balanced. I think it is perfectly okay to concentrate our energy on one aspect of our life (i.e., our job) for a period of time, but we must recognize that by saying yes to one thing (i.e., our career), means we are also inherently saying no in some way to the other aspects of our lives (i.e., family time, self-care, etc.). We can't do two things at the same time. Time is fixed and can only be divided so much before being completely diluted.
Pushing hard in one direction works for some people over a period of time... (I'd argue that some of the most influential and creative things came from obsessive people)... but we should be aware of what we're doing and how we're feeling regularly, so that we know when to step back and reassess the overall picture of our life and reprioritize.
As I start 2019 and return back home, I will not only be looking at the things/people I want to prioritize my yeses for, but I will also be looking to simplify, figuring out the things I can start saying no to.
Does this energize me? = YES.
Does this drain me? = NO.
Not only as we start a new year, but every moment we can decide to turn our lives around by committing to prioritize how we spend our time and energy.