Emotional intelligence is one of the most sought-after skills, and also among the hardest to learn.

Research dating back decades has found that emotional intelligence — the ability to manage your own feelings and the feelings of those around you — is the strongest predictor of success in the workplace. 

However, EQ isn't as easy to quantify as other skills because the characteristics that make it up, including empathy and self-awareness, are hard to measure.

You can assess and improve your EQ by paying closer attention to your conversations at work, says Juliette Han, a Harvard-trained neuroscientist and adjunct professor at Columbia Business School.

"Anything you can say that demonstrates empathy, curiosity, patience or self-awareness signals a high EQ," Han tells CNBC Make It. 

Here are three phrases those with higher emotional intelligence often use at work, according to Han:

'I appreciate your efforts'

People with a high EQ have a strong sense of social awareness and are committed to understanding the feelings of those around them. 

Acknowledging the hard work and dedication of your colleagues, especially if you weren't directly involved and/or benefitted from their efforts, shows that you genuinely value their contributions and want to foster a positive work environment, Han explains.

"Gratitude shouldn't be conditional, and emotionally intelligent people understand this well," says Han. "They recognize and congratulate someone on a job well done even if the work was behind the scenes, or they didn't personally gain from it, because they are compassionate and empathetic." 

'Let me know how you feel about it'

People with a high EQ might be able to read their co-workers' or boss's emotions, but they also take a beat before assuming how someone's feeling. 

"They appreciate the person's right to recognize their emotions on their own terms and give them space to do so," Hans explains. "At the same time, they offer their support and show they're ready to listen to those thoughts and feelings whenever the other person is ready to share."

With this phrase, you're creating a safe opening for the other person to share their thoughts or redirect the conversation. 

'I'm going to take some time to process'

A hallmark of EQ is self-regulation, or considering how to respond to strong emotions rather than acting on impulse. 

This phrase shows self-awareness and a clear attempt to regulate your emotions healthily before the conversation becomes unproductive or heated, Han explains. 

More importantly, this phrase allows you to revisit the conversation after some reflection, so you can come back to it with a calmer, more thoughtful response. 

"Having a high EQ doesn't mean suppressing or faking your emotions," says Han. "It's about understanding them and communicating those thoughts and feelings more effectively — which is a skill that can make everyone's job easier."

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