Although the meaning isn't related, the phrase "take the high road" probably comes from an old song from the 1800s, "The Bonnie Banks of Loch Lomond:" "Oh, you'll take the high road, and I'll take the low road, And I'll be in Scotland before you, But me and my true love will never meet again, On the bonnie, bonnie banks of Loch Lomond." In politics, to "take the low road" means to conduct an aggressive, negative, "dirty" political compaign--attacking the opponent in a personal way, making insinuations about possible scandals--financial or sexual--in the opponent's past, and so forth. To "take the high road" means to stick to positions on the issues, and policy; to be dignified; and to be civil and respectful toward your opponent. Here's an example of "taking the high road." In the 2008 presidential election, John McCain was Barack Obama's opponent. One of McCain's supporters said that she was scared of Obama. McCain replied: "I have to tell you. Senator Obama is a decent person and a person you don’t have to be scared of as president of the United States. He's a decent family man and citizen that I just happen to have disagreements with on fundamental issues and that's what this campaign's all about."

It is an idiom related to the idea that actions are ranked. "That was a low blow" means someone said something bad about you, and "be the bigger person" means you should act better (more mature) than someone. So "taking the high road" is similar, meaning to act better, more mature, or with more respect. It is usually the more difficult thing to do, because people will sometimes not act well when they are upset.

A useful resource https://www.urbandictionary.com/define.php?term=take%20the%20high%20road

Hi Gao Taking the high road means doing what is right, even if it is an unpopular choice or if it causes you problems. I think of it as something like "turning your cheek" which is not hitting back if someone hits you or not get revenge for something.