You know things are bad when your personal life is nonexistent. You frequently call home and tell your significant other not to wait for you for dinner. You disappoint your kids and friends when you cancel at the last minute. Sometimes, it's the cost of doing business. But if you're always feeling like you can't get everything done--and you're never seeing the people you love--you're doing something wrong.

A good place to start is realizing that you can't do it all. Elizabeth Grace Saunders, founder of Real Life E Time Coaching & Training and author of "How to Invest Your Time Like Money," writes in Harvard Business Review about how "optimizing in the micro day-to-day activities is not the same as optimizing in the macro as a measure of success." Instead of trying to get everything done, she says you should think about what matters most, focus on those tasks, and don't sweat the rest.

Saunders says when people don't know how to work smarter, they try to work harder. The result is that you sacrifice too many things in life and end up with "time regrets." The accumulation of time regrets, from missed dates with your significant other to a kid's graduation, will start to weigh you down mentally. "When you neglect to consider common time regrets, you not only put a lien on your future happiness, but you can also decrease your effectiveness in and enjoyment of the present," she writes.

Working smarter means consciously investing your time in the things that are most important. Not sure how to pull that off? Read Saunders' tips below.

Start investing your time smartly.

If you feel like you're a rudderless ship, floating from one urgent task to another by paddling frantically, you need to ask reevaluate how you're spending your time. Focus on the most important things and nothing else. "Start keeping a record of what you do by making note of key activities on your calendar or using a time tracking application, so you can begin to understand where you're spending your time and where you might need to adjust," she writes.

Don't let others pilfer your time.

People will steal your time if you let them. Everyday, hundreds of people are emailing and calling you, trying to schedule a meeting with you, give you the next big project, or just want to talk. It's up to you to protect your time. "If you allow external forces to always dictate your time investment then you're allowing others to steal your time," Saunders writes. "Practice saying 'no' to what's not most important to you so that you can invest in what is."

Stop de-prioritizing family and friends.

When you're on a deadline, your family and friends get pushed aside. But keep up the pattern of missed dinners and dates and you're headed for a lonely road. "A family dissolving doesn't often happen in a single large event. Instead it erodes with each choice to not make the people who love you a priority," she writes. "Engaging with friends and family can make life more fun and fulfilling, and provide an incredible amount of support during life's ups and downs. Get these activities on the calendar so that you have clarity on your firm commitments."

Stop skipping vacation.

"Relaxing is serious business. Be proactive in your vacation planning," Saunders writes. "Request time off at the beginning of the year instead of waiting to make a plan later. Otherwise, when 'later' comes, you'll again find yourself never leaving the office because you always feel like there is too much to get done." If you're the type of person who says vacation is for sissies, read the research. According to a nine-year study of 12,000 men at high risk of coronary heart disease, 32 percent were more likely to die of a heart attack if they skipped annual vacation time. The ones who skipped vacation also had a 21 percent increase of dying by any cause.

Give yourself time to reflect.

"In my experience, it's so easy to lose track of who you are, what you enjoy, where you are in life, and where you're going unless you purposely and intentionally take time to reflect," Saunders writes. "That could look like taking walks, journaling, praying, meditating, or simply staring at the ceiling for a while with no particular intention other than to be with yourself. In the end, if you never know who you are, it's hard to feel really good about yourself."