Since tension is bound to occur in friendships and relationships, it is crucial that you can express your feelings clearly. When you are owning and examining your feelings, you have the opportunity to handle this tension smoothly. And, speaking expressively will open space for other people to express how they feel, and work through these different feelings together.  Start by listening. Make sure to acknowledge what the person is saying before you counter with your own views. Use "I" statements. A simple way to avoid being too confrontational is to tell people what you're experiencing rather than what they're doing wrong. For example, you can say "When you're late to our coffee dates, I feel like you don't value my time" rather than "You're always late and it's really rude." As strange as it sounds, sometimes people don't know what's acceptable behavior. Acceptable behavior to one person can be unacceptable to another. In order for people to know what you are willing to put up with, be upfront and make it clear.  For example, if being late to coffee dates is your pet peeve, let them know. They might have no clue what effect their behavior has on you. If the person is really toxic, this strategy may not work, but it's good practice for setting boundaries regardless. This ties into effective arguing, but speaking assertively is something you can do all the time, whether you're arguing or not. Being an assertive speaker will help improve your communication and relationships.  Try to figure out where you could use some improvement. Maybe you're easily intimidated and people tend to step all over you, especially if they have a toxic personality. Identify the problem area as a first step. Reflect on tactics for specific situations. Maybe your toxic friend asks you for money and you have a hard time saying no. What can you do in these situations? Could you rehearse a simple script for the next time they ask? For example, you could say "I care about you, but I'm not able to give you any more money." Practice...

TL;DR in Vietnamese:
Thể hiện bản thân một cách hiệu quả. Cho họ biết về cách đối xử mà bạn hy vọng được nhận. Nói chuyện một cách cứng rắn và quyết đoán. Bảo vệ bản thân khỏi tổn hại. Xin lỗi khi phù hợp.