3 toxic phrases that highly successful people never use, according to psychologists and public speaking experts

Highly successful people often have at least one trait in common, psychologists say: Their inner monologues are positive and optimistic.

That can be a crucial element of achieving success: It's hard to achieve a goal or reach a milestone if you constantly tell yourself that you can't. Negative self talk can have a long-lasting impact over time, leading to anxiety, depression and a long-term hit to your confidence, research shows.

Here are three toxic phrases that successful people never say to themselves, according to psychologists and public speaking experts.

More than 80% of people face feelings of impostor syndrome in their lives, research shows. This can prompt you to use phrases like "I'm not worthy of my success" or "I don't deserve this," according to Christina Helena, a public speaking expert and TEDx speaker.

"Ask yourself: 'Why do I believe I don't deserve this?' If the answer is because your goals don't align with someone else's blueprint for success, acknowledge that feeling, and then let it go," Helena wrote for CNBC Make It last year.

"Once you identify where that attitude comes from, it will have less power over you," Helena added. "Success looks different for everyone. Ultimately, you get to decide whether you deserve the good in your life, and what you've worked so hard for. "

In a world where people constantly broadcast their life's highlights on social media without disclosing their hardships and setbacks, you may start to believe that other folks are better than you. 

Maybe you feel like you'll never measure up to the people you most respect and admire. You may tell yourself, "I'm not as good as them" or "I'll never have the life that they have."

"Rather than focusing on the fact that you're not as beautiful or funny or innovative as someone else, focus on what attributes you do bring to the table," Yale University lecturer Emma Seppälä wrote for Make It last month. "Maybe your jokes sometimes fall flat, but you're warm and people feel comfortable around you. You may not speak five languages, but your Excel spreadsheet skills are unparalleled."

If you need help finding things to admire about yourself, ask the people around you to share what they appreciate the most about you, Seppälä advised. It will "boost your resilience and can help open your eyes to how much you contribute to those around you and how much they appreciate you and your strengths," she wrote.

If you're constantly telling yourself, "I'm not changing" or "This is just who I am," you're limiting yourself from learning, according to psychologist and author Cortney Warren.

"People with low emotional intelligence are often more rigid and will fight efforts to shift or evolve," Warren wrote for Make It last year. "Strong convictions are important, but so is being open to new possibilities."

The next time you're presented with some feedback from your boss, try using this phrase instead, Warren suggested: "I need to think more about what you're saying. I want to be open to feedback about myself, even when it's hard to hear."

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