How to instantly become better at negotiating

• Sales strategist and The Sales Blog founder Anthony Iannarino shared his top tips for becoming less conflict averse.

• He said highly conflict averse people often struggle when pitching ideas or negotiating.

• Iannarino recommended taking up martial arts in order to gain perspective about your fears of conflict.

There's no room for doubt in a negotiation or a pitch.

And it's not enough to simply believe in what you're saying. You've got to look the part, too.

Anthony Iannarino, founder of The Sales Blog and author of "The Only Sales Guide You'll Ever Need" and "The Lost Art of Closing," said coming across as tentative is the biggest mistake you can make in any high-stakes conversation.

"You go to your boss, you have a really good idea, and you're not sold on it so you're nervous and tentative," he told Business Insider. "It's very hard for someone to say 'yes' to that."

But for people who typically avoid conflict at all costs, that's easier said than done. In some cases, defensive and timid body language can sabotage even the most highly convincing speech.

"I think it's very difficult to coach conflict averse people because it's sort of their default setting," Iannarino said.

So how can someone who hates conflict retrain their brain?

Iannarino said to take a martial arts class.

"The physical conflict makes you less afraid of verbal conflict for sure," he said.

He said getting into a physical conflict — in a safe, controlled setting, like a martial arts class — helps put things in perspective. Rejection and verbal conflicts simply become less of a concern.

"Nothing bad is going to happen to you," he said. "You might get a 'no'. You're going to be fine getting a 'no'."

Iannarino's theory is basically if you have the confidence to step onto the mat to spar with an opponent, you can definitely approach your boss to ask for a raise or pitch a big project.

"You lose your fear," he said. "Listen, you're not going to be in a physical conflict when you go to ask somebody for something. The bar in your mind is that something bad can happen to me. Almost nothing bad can happen to you. You can get a no and then you go back to professionally persisting."