• get to somebody / • Don't let (something) get to you.

• get to somebody
-(informal) to annoy or affect somebody
: ~를 괴롭히다, ~에게 영향을 미치다
: 'Get to you'라는 말은, 누군가를 화나거나 짜증 나게 만든다는 뜻이에요. 따라서, 누군가 'Don't let them get to you'라고 말을 하는 것은, 'Don't let them bother you. (걔네들 때문에 화내지 마.)'라는 뜻이랍니다. 
e.g.)
The pressure of work is beginning to get to him. 
업무 부담이 그를 괴롭히기 시작하고 있다.

A: My teacher is so bossy.
B: Hey, don't let her get to you. 

A: 우리 선생님은 너무 권위적이야.
B: 그 선생님 때문에 화낼 것 없어.



• Don't let somebody/something get to you.
If something bothers you, worries you, frustrates you, angers you, and so on, then you can also say that it "gets to you".
"Don't let _____ get to you" is a common piece of advice. It means that you shouldn't get too upset. Tell your friends or family members this when they have some kind of problem and seem to be in a bad mood about it. 

출처: 
https://redkiwiapp.com/ko/questions/Y2jyiJtwqIlvRE896NRP
https://www.phrasemix.com/phrases/dont-let-something-get-to-you